Automating Tasks with Visual Basic

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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.

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Nội dung Text: Automating Tasks with Visual Basic

Automating Tasks with Visual Basic
Introduction qWhen can’t find a readymade macro action that does the job you want, you can use Visual Basic code. qExample: − 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 qSome 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 §
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 qVisual Basic code is stored in database, but it need a different tool to view and edit it, called the Visual Basic editor. qOpen the Visual Basic editor: In the Access ribbon, choose Database § Tools➝ Macro ➝ Visual Basic
The Visual Basic Editor qThe 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 qIn the Visual Basic editor’s menu, choose Insert ➝ Module.
Adding a New Module qWhen add a new module, the Visual Basic editor automatically opens a code window that shows the contents of that module. qInitially, a brandnew 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 qBefore write code you should add one more instruction to the top of code file: Option Explicit qThis instruction tells Visual Basic to use stricter error checking, which catches common typos when using variables.
Simplest Possible Code Routine qEvery module are one or more subroutines. A subroutine is a named unit of code that performs a distinct task. qSubroutines start with the word Sub followed by the name of the subroutine and end with the statement End Sub qExample: Sub MyCodeRoutine() MsgBox "Witness the power of my code." End Sub
Module types qAccess 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 qOpen a form in Design mode. qTurn off Control wizard button. qAdd a new button. qIn the Property Sheet, choose the Event tab, and then select the button’s On Click event q Click the ellipsis (…) in the On Click Event box qSelect Code Builder and click OK