Excel and Visual Basic

Outline

Data exchange between Excel and Visual Basic.

Programming VB in Excel

Exchange data with .csv file .csv file is “comma separated value”

file. .csv file is plain text file. .csv file can only save one worksheet.

For multiple worksheets in a workbook, you need to use several .csv files.

You need do some editing to remove titles or labels before you use VB to read it.

Example

CodePrivate Sub Command1_Click()Dim payment(1 To 50) As Single, commission(1 To 50) As SingleDim index As IntegerOpen App.Path & "\commission.csv" For Input As #1

index = 1Do While Not EOF(1)Input #1, payment(index), commission(index)index = index + 1Loop

Close #1

End Sub

Using VB in Excel

Excel uses a special version of Visual Basic, which is called Visual Basic for Application (VBA)

User can use VBA to create customized Excel function (VBA procedures), which can be much more powerful than the build-in Excel functions.

Security issues

VBA procedures in Excel is also called Macros.

Macros are two-edged swords. Macros viruses are malicious VBA

procedures.

Setting the security level

Security Level High (default) Medium. We

should set the security to this level to run our VBA procedure.

Low (not recommended)

Medium level security If you set the security level to medium, every time

you open a Excel file containing macro, Excel will ask you if you want to enable the macro.

Example

VBA function code Function Comm(Sales_V  As Single) as Single

If Sales_V <500 Then Comm=Sales_V*0.03

Elseif Sales_V>=500 and Sales_V<1000 Then Comm=Sales_V*0.06

Elseif Sales_V>=1000 and Sales_V<2000 Then Comm=Sales_V*0.09

Elseif Sales_V>=200 and Sales_V<5000 Then Comm=Sales_V*0.12

Elseif Sales_V>=5000  Then Comm=Sales_V*0.15

End If End Function

Edit VBA program in Excel

Insert modules The VBA procedure

should be defined in a module.

If you don‘t have an existing module, create one by using the insert->Module menu.

Write code in visual basic editor

Final result

Passing a range of cells to VBA procedure The previous example shows how to

pass one value to a VBA function. However, in Excel it is possible to

pass several cells to a build-in function. E.g. SUM(a5:a7)

We call a5:a7 is a range. User defined VBA function can also

get a range of cells as input.

Data type: range

VBA defines a specific data type: range

Range is just like a object: it has properties.

Important properties of range Count : How many cells in the range Value : Value of the cell (it works

when range refers to only one cell)

Accessing individual cells

We use a special form of For…Next loop to access each cell in a range

Function meanvalue(InputRange As Range) As Single

Dim cl As Range

For Each cl In InputRange

‘some code here to get the value

‘cl.value keep the value of the cell

Next cl

End Function

Red word are key word in Visual Basic

Program task

Define a VBA function that calculate the average of a range of cells.

We define the function’s name as meanvalue.

codeFunction meanvalue(InputRange As Range) As SingleDim cl As Range ‘cl is used to get individual cellDim index As Integer, sum As Longindex = 1ReDim inputarray(1 To InputRange.Count) As SingleFor Each cl In InputRange

inputarray(index) = cl.Value ‘save cell value into arrayindex = index + 1

Next clsum = 0For i = 1 To InputRange.Count

sum = sum + inputarray(i)Nextmeanvalue = sum / InputRange.CountEnd Function

Use your defined VBA function