1

Quick Course of Visual Basic

for Excel

© J. Wach

Introduction 2

Visual Basic for Applications (VBA) is a programming language based on Visual Basic

(VB) implemented in MS Office applications and several others (AutoCAD, Solid Edge

etc.). This simplified version of VB is primarily used to automate work with

documents.

The main difference between VBA and VB is that VBA does not allow creating

independent EXE applications. The program code written in VBA is always included in

the document (i.e. XLS) created by some host program (i.e. Excel) and requires a

runtime environment for running, which is the host application that supports the

document. VBA is an add-on to host applications and is installed together with them.

VBA helps to build customized applications and solutions to enhance the capabilities

of host applications. The advantage of using VBA in Excel is that one can build very

powerful tools using linear programming.

Although the Excel provides a plenty of inbuilt functions virtually most of them are

business oriented and many functions suitable for engineering purposes are simply

not available. Therefore, they must be created by user in the form of Excel

formulas, but when the formulas are complex, they become illegible and

uncomfortable to use. In this case, using VBA to create user defined functions (UDF)

becomes the most obvious solution.

3Starting Visual Basic Editor - VBE

ALT – F11

1. Start the Excel

2. Open or create a new workbook

3. Save it as a XLSM file (file with macro-enabled workbook)

4. … and finally press

… to invoke VBE

NOTE.

Any time you press ALT-F11 you switch between VB

Editor and Excel worksheet

4Creating a new VB module in VBE

(3) … now enter

source code

(2)Then select

Insert Module

to open a new

module window

(1)In Project

Explorer panel

right click on

VBAProject (…)

to invoke popup

menu.

If you don’t want to be annoyed by popping up the error message window, do as follow:

Tools Options tab Editor and uncheck option - [ ] Auto syntax check,

Name the module 5

In Properties panel change the

name of the new module. Should be brief and self-explanatory

Settings 6

In case when someone needs to customize Excel in more elaborated way it would be

advisable to enable Developer ribbon menu.

To do this click: File Options, then click Customize the Ribbon tab and check

Developer and Click OK.

Optionally click here

to start VBE

First dummy function 7

Here is a comment

Keywords Identifier = Name

Use the new defined function in Excel formula 8

In a cell start typing

= du

and Excel displays a list of available functions among which you can find the new defined one. Press TAB to enter its name to formula window

After pressing the Enter key

you’ll see the result

returned by function in the

cell.

9Visual Basic (VB) language elements

Basic characters set (alphabet) used in VB tokens:

a b c d e f g h i j k l m n o p q r s t u v w x y z

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

0 1 2 3 4 5 6 7 8 9

_ . , : ’ = < > + - * / \ ^ ( ) [ ]% # $ @ ! & ” ;

Comments: a programmer-readable annotation in the source code, which areignored by interpreter during runtime. In VB comments are introduced by REM

keyword or by apostrophe and extends as far as the end of line. Examples:

REM This is comment and here all magic words loose its power

or 'Another way of inserting a comment here, the word żółć is OK

Within comment one can use any character than can be entered from a keyboard

even if it isn’t member of the VB character set.

Use comments. Without them, after some time, your own program will

become as mysterious as written by someone else. At least you should

put comment before every function in order to describe exactly its

application, usage, limitations, meaning of parameters, etc.

10Keywords

Keyword: a reserved word with special meaning in a particular context. In

VB cannot be used as an identifier, such as the name of a variable, function, or label. Keywords in VB are case insensitive therefore REM, Rem and rem are

the same

Some VB keywords (minimal set):

REM,

DIM, AS, BOOLEAN, BYTE, INTEGER, LONG, SINGLE, DOUBLE, STRING,

LET, SIN, COS, TAN, ATN, EXP, LOG, SQR, SGN, ABS, RDN, INT, FIX

TRUE, FALSE, IF, THEN, ELSEIF, ELSE

FOR, TO, STEP, NEXT, DO, LOOP, WHILE, UNTIL, WEND

FUNCTION, EXIT, END

In VB keywords are used to build statements. Each statement begins

with some keyword.

11Identifiers (names)

Names are given by programmer to different entities such as variables, functions, types

etc. In VB it is a sequence (max 255 char.) of letters (in Excel VBA diacritical characters

are allowed), digits and the underscore „_” character. Names must begins with an

letter, and must be different from any VB keyword. Identifiers are case insensitive.

In VB variable or function identifier can be suffixed by one of the following characters:

% & # ^ ! $ @

These are identifier type characters, which determine only an item data type, and are not

a part of an identifier.

Examples:

Correct VB identifiers:

dT ≡ dt (hence dT/dt always equals 1 because of case insensitivity)

A1, p_max, pi, temperature, długość (!! this is Ok), ...

Wrong VB identifiers (errors are marked with red)

1A, a?, person█name, temp^2

… and suggestions how to correct them

nr_1A, a_question, person_name or PersonName, temp_2

Statement 12

A statement is a syntactic unit of programming language. In VB statements are used to control

workflow, build definition, declaration, and instructions.

A program in VB (called source code) is simply a sequence of statements.

Statement must occupy one line, but with underscore “_” character, which is line-

continuation character, preceded by space one can break too long statement into two or more

lines.

Several statements can be placed in one line, but then they must be separated by colon “:”

Examples: 'Constant definition

Const pi = 3.141592

'Variable declaration

Dim time, omega As Double

'Assignment statement (instruction)

Let time = 1/(2*pi*f)

'Many statement in one line separated by colon :

Dim f As Double: Let f = 100.0

Let omega = 2*pi*f: Let time = 1/omega

'One long statement . . .

Let a = 1.000023*x + 0.374091*y + 0.096784*z + 0.278868/v

'. . . broken down into many lines

Let a = 1.000023 * x _

+ 0.374091 * y _

+ 0.096784 * z _

+ 0.278868 / v

Returning result to formula 13

In order for a function to return a specific result,

somewhere in the function body, must be at least

one assignment statement that assigns the result

of the calculation to the function identifier. That

value will be returned to the call location. The

syntax is:

LET fun_name = expression

Without this, function will always return the zero

value, what is default behavior. The keyword LET

can be omitted.

This is numerical literal

Literal 14

A literal is a sequence of characters that represents fixed value in source code like

number, text string, date and other.

Integer literal – used to represent integer numbers. It is a sequence of decimal digits preceded if

necessary with minus or optionally with plus character.

+125 ≡ 125 ; -456 ; 30113 ; 000123 ≡ 123 …

Characters: % & and ^ forces respectively INTEGER, LONG or LONGLONG type:

125% 125& 125^ the same number 125, but of different type (and size)

Floating point literal – used to represent rational numbers in decimal form. It is compound of two

sequences of digits, representing respectively integer and fraction part of a number, preceded if necessary

with sign character („–”, „+”) and separated by dot. The plus character can be omitted if the number is

positive. Either integer or fraction parts may be omitted if any of them is equal to zero, but the decimal

separator (dot) must remain.

Another way is to write it in the significand–exponent form (scientific notation) i.e. if m – significand

(integer or floating point literal) and c – exponent (integer literal) then literal has form mEc and represents

value m∙10c.

+125.0 ≡ 125.0 ≡ 125. ; -124.567 ; 0.001234 ≡ .001234 ≡ 0.00123400

0.0 ≡ 0. ≡ .0 floating point zero

1.0E+03 ≡ 1E3 ≡ 10E2 ≡ 100E1 ≡ 1000.0 ≡ 1000. one thousand1.23E+03 ≡ 12.3E+2 ≡ 123.0E1 ≡ 123E1 ≡ 1230.0 1.23∙103 = 1230.0

Characters ! and # forces respectively SINGLE lub DOUBLE type:

125.0! ≡ 125! 125.0# ≡ 125# the same number 125, but of different type (and size)

Literal cont. 15

Date literal – (represents date and time) a sequence of characters enclosed between pair of hash

characters #...#

#1 February 1950#

#01.02.1950#

#1 May 2014 12:35#

String literal – represents text which can be displayed on screen. This is a sequence of characters

enclosed between pair of double-quote characters “…”. Between them one can put any ASCII

character, which can be entered from keyboard including diacritical characters. Upper and lower

case letters are distinguishable. String literal can be empty “”.

"This is some text, in which one can put any printable character "

If double-quote character is to be part of the string, then it must be doubled.

"The title of the film is ""Invincible""" right

"""" represents single double-quote character (!!)

"The title of the film is "Invincible"" wrong because

this is interpreted as string "The film title is "

followed by some illegal token: Invincible""

Function with single parameter 16

The function takes one parameter which is

listed between parenthesis (here is “x”) and

carries out some calculation (here 2x +1)

which result is returned to formula. Syntax:

fun_name ( list_of _par )

dummy_par(x)

This is variablenamed „x”

Whenever you make any amendments to your code you should press

Ctrl + Alt + F9 to force recalculation of all worksheets.

Variables 17

A variable is a memory location (identified by a memory address) paired with an associated

symbolic name (an identifier), used to hold some data value that can be changed during

execution.

There are two things one can do with a variable: read it – take a value stored in it, or write to it

– replace an old value by new one. A variable is read whenever it is used in expression. Reading

doesn't change the value stored in it, but writing does. To write new value to variable one should

use an assignment statement in the following form:

LET variable_name = expression

variable_name = expression

or simpler form

where:

variable_name - variable identifier

expression – some sort of expression e.g. mathematical

Expressions 18

An expression is a sequence of literals, operators, variables, functions, constants and parenthesis that

describes the way the data is to be processed (calculated). In case of mathematical expressions, calculation

are done according to operators precedence, which can be altered by round brackets – parenthesis ( ). No

other type of bracket - like square [ ] or curly { } - can be used in this role.

(2) Arithmetical operators

(descending precedence)

Examples

Rise to power (^) a ^ 2, a ^ 0.5

Opposite value (-) -a

Multiplication, division (*, /) a*b, 2*a, a/b (11/2 = 5.5)

Integer division (\) a\b (11\2 = 5)

Modulo division (mod) a mod b (10 mod 3 = 1)

Addition, subtraction (+,-) a+b, a-b

(4) Logical operators

(descending precedence)

Examples

Negation a (not) NOT a

Conjunction a b (and) a AND b

Disjunction a b (or) a OR b

Exclusive disjunction (xor) a XOR b

Equivalence a b (eqv) a EQV b

Implication a b (ipm) a IMP b

(3) Comparison operators (equal precedence) :

equal =, non-equal <>

greater then >, less then <,

greater or equal >=, less or equal <=

(1) Functions (equal precedence) Examples

Trigonometric: sin(x), cos(x), tan(x), arctan(x) sin(x), cos(x), tan(x), atn(x)

Exponent ex = exp(x) and natural logarithm ln(x) (!!) exp(x), log(x)

Absolute value |x| and sign sgn(x) abs(x), sgn(x)

Square root 𝑥 sqr(x) or x^0.5

Integer part of a number [x] int(x) (< x), fix(x) (>x for x<0 and <x for x>0)

Random number rnd, randomize (seed function)

Expressions - evaluation order 19

Evaluation order: In the first place subexpressions in parenthesis and functions, then arithmetic

operators, then comparison operators and in the end logical operators. Operators are evaluated

according to their precedence. In case of equal precedence they are evaluated from left to right

(left-associative). Evaluating precedence can be altered by parenthesis. In case of nested

parenthesis most nested expression are evaluated as first.

x = x + 1

4/2*12/4 is evaluated as ((4/2)*12)/4 (2*12)/4 24/4 6

NOTE: left-associativity of rise to power operator, and (!) spaces preceding the ^

character

4 ^ 3 ^ 2 is evaluated as (4 ^ 3) ^ 2 64 ^ 2 4096

but not like this (4/2)*(12/4) 3*4 6

NOTE: this is not meaningless

this increases x value by one

x = x - 1 similarly this decreases x value by one

x = 2 * x this increases x value two times

but not like this 4 ^ (3 ^ 2) 4 ^ 9 262144

4*(1+2*(3+4)) is evaluated as 4*(1+2*(3+4)) 4*(1+2*7) 4*(1+14) 4*15 60

4*[1+2*(3+4)] wrong, only round brackets can be used

Expressions - mathematical formula transcription examples 20

𝑎 + 𝑏

𝑐 + 𝑑(a+b)/(c+d)

−𝑏 + 𝑏2 − 4𝑎𝑐

2𝑎

(-b+sqr(b^2-4*a*c))/(2*a)

(-b+sqr(b*b-4*a*c))/2/a

𝑎

𝑏 + 𝑐a/(b+c) 𝑎 + 𝑏

𝑐(a+b)/c

𝑎 + 𝑏

𝑐 𝑑=𝑎 + 𝑏

𝑐

1

𝑑

(a+b)/(c*d)

(a+b)/c/d

sqr(2*k*p/((k-1)*ro)*(1-(p0/p)^((k-1)/k)))

sqr(2*k/(k-1)*p/ro*(1-(p0/p)^((k-1)/k)))

2𝜅

𝜅 − 1

𝑝

𝜚1 −

𝑃0𝑝

(𝜅−1)/𝜅

a = 1.000023 * x _

+ 0.374091 * y _

+ 0.096784 * z _

+ 0.278868 / v

a+b/c 𝑎 +𝑏

𝑐

Too long expressions can be broken into two or more lines using underscore “_” character preceded by space as in thisexample:

a = 1.000023 * x + 0.374091 * y + 0.096784 * z + 0.278868 / v

𝑎 + (−𝑏)

a – b

a + -b

a + (-b)

-b + a

𝑎𝑏

𝑐𝑑

a*b/(c*d)

(a*b)/(c*d)

a/c*b/d

Function with many parameters 21

The function takes two parameters which are listed

between parenthesis (here they are “a” and „b”)

and calculates hypotenuse "c" in right triangle of

sides a, b and c according to Pythagorean theorem.

dummy_2(a, b)

Syntax:

fun_name ( list_of _par )

𝒄 = 𝒂𝟐 + 𝒃𝟐

Note: in some non-English Excel versions not colon, but semicolon is used as an argument separator in function call.

Data types 22

Type Range Size [B]

BYTE 0 .. 255 (1-3 digits accuracy) 1

INTEGER -32768 .. 32767 (4-5 digits accuracy) 2

LONG -2147483648 .. 2147483647 (9-10 digits accuracy) 4

LONGLONG -9223372036854775808 .. 9223372036854775807 (±1019) (18-19 digits accuracy) 8

SINGLE ±1,5∙10-45 .. ±3,4∙1038 (8 digits accuracy) 4

DOUBLE ±5,0∙10-324 .. ±1,7∙10308 (16 digits accuracy) 8

The data type (simply type) is a set of values that data can have. The data type determines which

operation can be performed and how its values are represented in memory. In VB there are primitive

types and composite types. The primitive types represent values that cannot be broken down into

smaller components. Composite types are values that are collection of some values which can be both

primitive or composite types. Bellow list of VB primitive types:

Numerical types: (green - integer, red - floating point types)

Logical type:

BOOLEAN can poses one of the two values TRUE or FALSE

e.g. 2 > 3 FALSE, 2 <> 3 TRUE, 2 = 3 FALSE …

Text string type:

STRING represents text of variable or fixed length

Type declaration 23

It is not obligatory, but highly recommended to declare variables, constants and functions.

Declarations saves execution time and memory space. Undeclared variables are called variants

and occupy more space in memory. They should be used only when a variable is planned to hold

data of different type. If the data type is well known then every variable should be declared.

Declaration syntax:

DIM varaibles_list AS Type

Where: varaibles_list – a list of variables’ names separated by coma, Type – type keyword

(integer, long, single, double, Boolean etc.) or type identifier.

’ Declaration of identifiers a, b as

’ double precision floating point variables

DIM a, b AS Double

’ and this is equivalent to

DIM a AS Double

DIM b AS Double

With identifier type characters (% & ^ ! # $) declaration can be simpler. It is sufficient to suffix

an identifier with type character first time when it appear in the code. Examples:

Dim i As Integer i%

Dim n As Long n&Dim x As Single x!

Dim y As Double y#

24Declaration examples

Function sinh(x as double) as double

sinh = (exp(x) - exp(-x))/2#

End Function

Function sinh#(x#)

sinh = 0.5*(exp(x) - exp(-x))

End Function

sinh 𝑥 =e𝑥 − e−𝑥

2

Function sinh(x)

sinh = (exp(x) - exp(-x))/2.0

End Function

Function diag (a as double, b as double) as double

diag = sqr(a^2 + b^2)

End Function

𝑑(𝑎, 𝑏) = 𝑎2 + 𝑏2

- acceptable but not recommended

- alternative way with identifier type characters (here

character # is used do declare double type)

- recommended way

One argument function

Two or more arguments

function

Block diagrams 25

START

Instruction

a, b …

Condi

-tion

x, y, …

STOP

Condition

11

Terminating place

Line indicating

workflow direction

Data input box

Instructions box

Algorithm branching

Output results

Beginning of an algorithm

Line connector used when line has

to be broken for clarity reason(between pages or within page)

or

SubroutineSubroutine calling

A block diagram is a specialized,

high-level flowchart used in

programming. Its structure provides

a high-level overview of major

algorithm components, and

workflows branching.

The block diagram is used to present

the general idea of an algorithm

without referring to any specific

programming language.

26An algorithm for finding roots of a quadratic equation

Block diagramThe algorithm

𝑓 𝑥 = 𝑎𝑥2 + 𝑏𝑥 + 𝑐

Δ = 𝑏2 − 4𝑎𝑐

1. Get the input parameters: a, b, c

2. Calculate a discriminant

3. Test the D value

a. If D < 0 then no solution is

available

b. If D = 0 then there is one

solution x0

𝑥0 = −𝑏

2𝑎

c. If D > 0 then there are two

solutions x1 and x2

𝑥1 =−𝑏 + √Δ

2𝑎𝑥2 =

−𝑏 + √Δ

2𝑎

Branching - conditional statement IF THEN 27

Instruction_1

Instruction_2

...

Instruction_3

Condition

T

F

X = -15

...

IF X < 0 THEN X = -X

... ' here x=15

Example:Instruction_1

IF condition THEN Instruction_2

Instruction_3

min = 15

max = -1

...

IF min > max THEN x = max: max = min: min = x

... ' Now min=-1 a max=15

Exchanging values between two variables min and max, when min > max.

many instructions can be separated by ":„

and such a sequence is treated as one

min max

x

2

13

Exchanging Algorithm between

min i max with the help of

auxiliary variable x

X = ABS(X)

Function vb_abs(x As Double) As Double

If x < 0 Then x = -x

vb_abs = x

End Function

Instruction_1

IF condition THEN

Instruction_2

...

END IF

Instruction_3

X = -15

...

IF X < 0 THEN

X = -X

END IF

...’here x=15

𝑥 = ቊ−𝑥 when 𝑥 < 0𝑥 when 𝑥 ≥ 0

Condition = Boolean expression resulting in the

values True or False i.e. (x<0 OR 1<x)

Branching – conditional statement IF THEN ELSE 28

Instruction_1

Instruction_3

...

Instruction_4

condition

Instruction_2

...

T F

Instruction_1

IF condition THEN

Instruction_2

...

ELSE

Instruction_3

...

END IF

Instruction_4

Function vb_sgn(x As Double) As Double

If x < 0 Then

vb_sgn = -1#

Else

If x > 0 Then

vb_sgn = 1#

Else

vb_sgn = 0

End If

End If

End Function

Examples:

Function sinc(x As Double) As Double

If x = 0 Then

sinc = 1#

Else

sinc = Sin(x) / x

End If

End Function

sinc 𝑥 = ቐ1 when 𝑥 = 0sin 𝑥

𝑥when 𝑥 ≠ 0

This is nested sequence of IF THEN ELSE statements. See next page how to make it simpler

sgn 𝑥 = ቐ−1 when 𝑥 < 00 when𝑥 = 01 when𝑥 > 0

Branching – conditional statement IF THEN ELSEIF ELSE 29

condition1

Instruction_1

T F

Function vb_sgn(x As Double) As Double

If x < 0 Then

vb_sgn = -1#

ElseIf x > 0 Then

vb_sgn = 1#

Else

vb_sgn = 0

End If

End Function

Note! "ELSEIF" is not the same as "ELSE IF"

condition2F

conditionN_1

Instruction_2

Instruction_n_1

T

T

F

. . . .

. . . .

. . . .

Instruction_n

IF condition1 THEN

instruction_1

ELSEIF condition2 THEN

instruction_2

. . . .

ELSEIF conditionN_1 THEN

instruction_n_1

ELSE

instruction_n

END IF

ELSE part is optional

In case when chain of if then else if then … is to be used VB offers

compact version o IF statement

Loop statement DO LOOP – condition at the beginning 30

Instruction_1

Instruction_2

....

Condition

Instruction_3

Instruction_1

DO WHILE condition

Instruction_2

...

LOOP

Instruction_3

fact = 1

i = 1

DO UNTIL i > n

fact = fact * i

i = i + 1

LOOP

This condition tells when to stay in the loop

This condition tells when to get out of the loop

Instruction_1

DO UNTIL condition

Instruction_2

...

LOOP

Instruction_3

fact = 1

i = 1

DO WHILE i <= n

fact = fact * i

i = i + 1

LOOP

Example, calculating factorial of n i.e n! = 1∙2 ∙3 ∙ ... ∙ n

T, F

F, T

T

F

or NOT i <= n

Instruction_1

WHILE condition

Instruction_2

...

WEND

Instruction_3

Function vb_fact(n As Byte) As Double

Dim res As Double

Dim i As Byte

res = 1

i = 1

Do Until i > n (Do While i <= n )

res = i * res

i = i + 1

Loop

vb_fact = res

End Function

Instruction_1

WHILE NOT condition

Instruction_2

...

WEND

Instruction_3

Loop statement DO LOOP – condition at the end 31

Instruction_1

DO

Instruction_2

...

LOOP WHILE condition

Instruction_3

Instruction_2

...

Instruction_3

ConditionT, F

F, T

Instruction_1

DO

INPUT "X = ", X

LOOP WHILE X <= 0

Example: How to prevent from entering to variable x a non-positive value

DO

INPUT "X = ", X

LOOP UNTIL X > 0

Instrukcja_1

DO

Instrukcja_2

...

LOOP UNTIL condition

Instruction_3

This condition tells when to stay in the loop

This condition tells when to exit the loop

T

F

Function vb_input() As Double

Dim x

Do

x = Application.InputBox("Enter positive number")

Loop While x <= 0

vb_input = x

End Function

Loop statement DO LOOP – condition somewhere inside 32

Instruction_2

...

Instruction_4

ConditionT

F

Instruction_1

Instruction_1

DO

Instruction_2

...

IF Exit_condition THEN EXIT DO

...

Instruction_3

LOOP

Instruction_4

EXIT DO statement is design to exit a loop from any place

inside it. Typically, it is combined with IF THEN statement

with condition which has to be fulfilled to break the loop.

Can be combined with WHILE and UNTIL

. . .

Instruction_3T

Repeating a group of statements a specified number of times - FOR 33

Instruction_1

j = start

DO WHILE j <= Max

Instructions_2

j = j + step

LOOP

Instruction_3

j j + step

Instruction_3

j <= max

T

F

Instructions_2

j start

Instruction_1

Instruction_1

FOR j = start TO Max STEP step

Instructions_2

NEXT j

Instruction_3

Instruction_1

FOR j = 1 TO Max

Instructions_2

NEXT

Instruction_3

Case: start=1, step=1. Loop is

executed Max number of

times

fact = 1

FOR i = 2 TO n

fact = fact * i

NEXT

Note:The section STEP can be omitted when step = 1.

Loop counter after NEXT can be also omitted.

In this loop an instruction set is executed

specified number of times. Here, the

repetition is controlled by auxiliary variable

j (loop counter) which name is given by

programmer.

Alternative realization by

DO … LOOP statement

Example factorial of n

Constants definition 34

In computer programming, a constant is a value that cannot be altered by the program

during normal execution, i.e., the value is constant. When associated with an identifier,

a constant is said to be "named," although the terms "constant" and "named constant" are

often used interchangeably. It is advisable to use constants instead of literals or constant

expressions (i.e. expressions where no variable are used) as it makes source code more

clear, readable, flexible, and easier to maintain.

Syntax: CONST const_name = constant_expresion

or

CONST const_name AS type = constant_expresion

Example: CONST pi = 3.141592

CONST deg = pi / 180#

CONST pi_2 AS DOUBLE = pi / 2

’ This is wrong as it invokes function. In constant expression only constant’ values can be used

CONST pi = 4 * ATN(1)

Example: Sun azimuth calculation 35

Const pi = 3.14159265358979 'can be also computed as pi = 4 * Atn(1)

Const deg = pi / 180# 'to transform angles known in degrees into radians e.g. 15*deg

' The Sun azimuth in radians

'---------------------------------

' Input:

' day - day number 1 .. 365

' hangle - hour angle in radians

' lat - latitude in radians

' Result:

' the sun angular altitude (above horizon) in radians

'

Function SunAzim(day As Double, hangle As Double, lat As Double) As Double

Dim beta As Double ' the Sun altitude

Dim decl As Double ' the Sun declination

Dim azim As Double ' the sun azimuth candidate

Dim cosw As Double ' cosine of hour angle for the Sun on West

decl = 23.45 * deg * Sin(2 * pi * (day - 81) / 365#)

beta = Cos(lat) * Cos(hangle) * Cos(decl) + Sin(lat) * Sin(decl) ' this calculates sin(beta)

beta = Application.WorksheetFunction.Asin(beta) ' and this calculates beta

cosw = Tan(decl) / Tan(lat)

azim = Cos(decl) * Sin(hangle) / Cos(beta)

azim = WorksheetFunction.Asin(azim)

If (Cos(hangle) >= cosw) Then

SunAzim = azim

Else

If (azim >= 0) Then

SunAzim = pi - azim

Else

SunAzim = -pi - azim

End If

End If

End Function

If some Excel function has to be used, that is not defined in VB

like arcsin(x), then instead of defining the function on the

basis of some mathematical identity, one can call it by

refereeing to a special object Application as in the following

example:

Application.WorksheetFunction.asin(…)

or

WorksheetFunction.asin(…)

where asin is an Excel arcsin(..) function.

References 36

[1] https://www.exceltrick.com/excel-vba-basics/getting-familiar-with-vbe/

[2] https://msdn.microsoft.com/en-

us/library/office/ee814737%28v=office.14%29.aspx#odc_Office14_ta_GettingStartedWit

hVBAInExcel2010_VBAProgramming101

[2] Excel 2010 Developer Reference

https://msdn.microsoft.com/en-us/library/office/ff846392%28v=office.14%29.aspx

[3] Visual Basic for Applications language reference for Office 2010

https://msdn.microsoft.com/en-us/library/office/gg278919%28v=office.14%29.aspx

[4] Visual Basic for Applications language reference for Office 2013

https://msdn.microsoft.com/en-us/library/office/gg264383%28v=office.15%29.aspx

[7] MS Office Dev Center:

https://docs.microsoft.com/en-us/office/vba/excel/concepts/events-

worksheetfunctions-shapes/list-of-worksheet-functions-available-to-visual-basic

[8] Excel and VBA Solutions - http://www.globaliconnect.com/excel/

[9] https://docs.microsoft.com/pl-pl/office/vba/language/glossary/vbe-glossary#variable