Introduction When can’t find a readymade macro action that does the job you want, you can use Visual Basic code. Example: − Modify a whole batch of records at once. − Perform complex calculations. − Interact with other programs on computer. − Write even more complicated validation routines that lock out bad data.
Understanding VBA Terminology Some basic VBA terminology: − Statement: A word or combination of words that constitutes an instruction to be performed by the VBA engine. − Procedure: A collection of VBA statements that are grouped together to perform a certain task. There are two types of procedures: Subroutines: perform a single task, no return. Functions: perform a task and then return a value
Understanding VBA Terminology− Module: Procedures live in modules. A module consists of one or more procedures− Variable: is nothing more than a name applied to represent a data value. Variable is used to hold values such as customer names, dates, and numeric values manipulated by the VBA code.
The Visual Basic Editor Visual Basic code is stored in database, but it need a different tool to view and edit it, called the Visual Basic editor. Open the Visual Basic editor: In the Access ribbon, choose Database Tools➝ Macro ➝ Visual Basic
The Visual Basic Editor The Visual Basic editor window is divided into three main regions. − Project window: shows all the modules in your database. − Properties window: which shows settings for the currently selected item in the Project window. − Document window: Edit code region.
Adding a New Module In the Visual Basic editor’s menu, choose Insert ➝ Module.
Adding a New Module When add a new module, the Visual Basic editor automatically opens a code window that shows the contents of that module. Initially, a brand-new module has just one line of code: Option Compare Database − This line is an instruction that tells Visual Basic how to handle operations that compare pieces of text.
Adding a New Module Before write code you should add one more instruction to the top of code file: Option Explicit This instruction tells Visual Basic to use stricter error checking, which catches common typos when using variables.
Simplest Possible Code Routine Every module are one or more subroutines. A subroutine is a named unit of code that performs a distinct task. Subroutines start with the word Sub followed by the name of the subroutine and end with the statement End Sub Example: Sub MyCodeRoutine() MsgBox "Witness the power of my code." End Sub
Module types Access stores code in two places: − Class modules: attached to the form or report, it executes when the form or report is opened, the class module does not appear in the modules section. − Standard modules: Code can also be stored in modules section. Standard modules is accessible to all objects in your database.
Responding to a Form Event Open a form in Design mode. Turn off Control wizard button. Add a new button. In the Property Sheet, choose the Event tab, and then select the button’s On Click event Click the ellipsis (…) in the On Click Event box Select Code Builder and click OK