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Automating Tasks with Visual Basic. 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 .
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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. • Inthe Property Sheet, choose the Event tab, and then select the button’s On Clickevent • Click the ellipsis (…) in the On Click Event box • Select Code Builder and click OK