MS-Access / Getting Started

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Controlling the Flow of Statements

Visual Basic provides many ways for you to control the flow of statements in procedures. You can call other procedures, loop through a set of statements either a calculated number of times or based on a condition, or test values and conditionally execute sets of statements based on the result of the condition test. You can also go directly to a set of statements or exit a procedure at any time. The following sections demonstrate some of (but not all) the ways that you can control flow in your procedures.

Call Statement

Use a Call statement to transfer control to a subroutine.

Syntax

Call subroutinename [(<arguments>)]
or
subroutinename [<arguments>]

where <arguments> is

{[ByVal | ByRef] <expression> },...

Notes

The Call keyword is optional, but if you omit it, you must also omit the parentheses surrounding the parameter list. If the subroutine accepts arguments, the names of the variables passed by the calling procedure can be different from the names of the variables as known by the subroutine. You can use the ByVal and ByRef keywords in a Call statement only when you're making a call to a dynamic link library (DLL) procedure. Use ByVal for string arguments to indicate that you need to pass a pointer to the string rather than pass the string directly. Use ByRef for nonstring arguments to pass the value directly. If you use the ByVal keyword to declare an argument, Visual Basic passes a copy of the argument to the subroutine. The subroutine cannot change the original variable in the calling procedure.

If you use the ByRef keyword, Visual Basic passes the actual memory address of the variable, allowing the procedure to change the variable's value in the calling procedure. (If the argument passed by the calling procedure is an expression, Visual Basic treats it as if you had declared it by using ByVal.)

Examples

To call a subroutine named MySub and pass it an integer variable and an expression, enter the following:

Call MySub (intMyInteger, curPrice * intQty)

An alternative syntax is

MySub intMyInteger, curPrice * intQty