XP New Perspectives on Microsoft Office Access 2003 Tutorial 11 1 Microsoft Office Access 2003 Tutorial 11 – Using and Writing Visual Basic for Applications

New Perspectives on Microsoft Office Access 2003 Tutorial 11

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XP

Microsoft Office Access 2003

Tutorial 11 – Using and Writing Visual Basic for Applications Code


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XPLearn about VBA

• When you work in Access, in the background, Visual Basic for Applications (VBA) code is being created.

• You can also write your own VBA code that will alter the properties of objects, perform calculations, and many other custom actions.

• Recall that an event is something that happens while using the database.

• You can write a statement that, when an event occurs, responds by executing a series of VBA statements.


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XPFunction procedures, Sub procedures, and modules

• Statements are grouped together into procedures, which can be either a function or a Sub procedure.

• Common procedures are usually stored together into a module.

• A module can be a standard module (stored in memory with other database objects) or it can be a class module (stored in association with a particular form or report).

• With class modules, the procedures are available by the form or report for which the class module was created.


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XPThe structure of a VBA module


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XPLearning VBA takes time and effort

• Learning to write VBA code efficiently and accurately is the hardest part of learning to use Access.

• In this tutorial, you are getting just a small view of VBA code.

• You should keep in mind that you will not be considered a proficient VBA programmer following this tutorial.

• Rather, if you want to be a database developer, you should probably take another course geared towards VBA programming.


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XPReview and modify an existing Sub procedure in an event procedure

• When a class module already exists, you can view the code for the procedures in the VBA editor: – Open the property sheets for the object and then locate

the event for which the procedure is written

– Click the Build button to open the Visual Basic window, which reveals the code stored in the class module

• The window in which the code appears is called the Code window.


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XPUse assignment statements

• Procedures are enclosed between the Sub statement and the End Sub statement.

• Within a procedure, you will see statements that work together called control structures.

• Assignment statements assign a value to a field or property.

• In some cases, an assignment statement might assign a new value to an object property.

• You can make changes to VBA code in the Code window.


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XPEvent properties for a form


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XPThe Visual Basic Code window


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XPRecognize VBA statements

• In the Code window (shown in the previous slide) you would view, edit, and test your VBA statements.

• You will probably not understand the statements that appear in this window.

• However, there are a couple of statements that you will recognize: – The first statement is the Private Sub statement

– The last statement is the End Sub statement

• In this sample code, the ForeColor is changed under certain circumstances. – The code used the RGB function, which will return a specified colored by

using combinations of Red, Green, and Blue


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XPA function that modifies an object’s color


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XPRGB values for some colors


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XPCreate Function proceduresin a standard module

• To create new procedures click Modules on the objects bar and then click New.

• This will open the Code window in the Visual Basic window.

• To write a Sub procedure,begin with the Sub statement.

• To write a Function procedure, begin with the Function statement.

• The Function will end with the End Function statement.


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XPAssign a name to a function

• The Function statement is then followed with the name of the function.

• If you will be passing values to the Function, the Function name is followed by a Parameter list (which could be just one item).

• When you pass a value to a Function, it is called an argument.

• When naming a Sub procedure or a function, you must follow the rules for naming objects.


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XPDefine a function in the Code window


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XPName and save your module

• Once you have written your Function, you will need to save the module that holds the function.

• When you click the Save button, you will be prompted to supply a name for the module.

• This is not the same as naming the Function and you do not have to follow the name rules mentioned previously.

• Recall that a module will hold a collection of procedures so you will want to name the module something that will indicate what is inside the module.


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XPUse comments in your functions


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XPCreate event procedures

• VBA is an event-driven language, meaning that when events takes place, procedures are triggered.

• All event procedures are Sub procedures. • Access will automatically name the event in a

standard way, which includes: – The name of the control

– An underscore

– The event name


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XPAdd an event procedure

• To add an event procedure to a class module:– Open the object to which it will be attached

– Open its property sheet

– On the Event tab, select the event that will trigger the function

• This will open the code window for the object you have selected.

• Before you run your procedure, it must first be compiled.

• The process of compilation is the process of converting the code to a format the computer can understand.


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XPUse the If statement

• A commonly used control structure is the If statement

• The If statement provides a condition and then if the condition is true, a set of statements is executed; if it is false, a different set of statements is executed.

• The If statement created in your tutorial incorporates the IsNull function into it.

• The IsNull function returns a True value if the argument is empty (no text) and it returns a False value if the argument is not empty.


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XPAn example of an If statement


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XPThe function execution process


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XPAn example of an event procedure


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XPDeclare variables in functions and procedures


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XPPrimary VBA Data Types


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XPCompile and test Function procedures, Sub procedures and event procedures

• When you compile a module, Access will look for errors in syntax.

• If any errors are found, an error message will display. You will need to fix all syntax errors before the modules can complete compilation.

• When no errors exist, Access will translate the procedure.

• You should compile a module any time you make changes to make sure there are no syntax errors in its procedures.

• You should also test each procedure to make sure it performs as you expect.


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XPModify object properties in VBA code

• Sometimes you will want values in your database to appear differently in certain circumstances.

• For example, you might want unpaid balances to appear in red and paid balances to appear in green.

• You might also want to hide a control under certain circumstances but display it in other circumstances.

• These kinds of things can be accomplished with VBA statements.


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XPHide text and change display colors

• The ForeColor property of an object represents the color of the text in the object.

• You can write statements that will alter this property when a certain condition arises

• The Visible property of an object is set to True when you want the object to be displayed and False when you want it hidden.

• This property can be altered by writing VBA statements to change the property under certain circumstances.

• Finally, you can use the DoCmd statement to execute an action in a function.


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XPHiding and Changing Display Colors


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XPAn event procedure to modify properties

Documents

XP New Perspectives on Microsoft Office Access 2003 Tutorial 11 1 Microsoft Office Access 2003 Tutorial 11 – Using and Writing Visual Basic for Applications