Knowledge Base Articles » KB100222: When to Use Parentheses with a Subroutine or Function in VB/VBA/VBScript.

When to use, or not to use, parentheses ( ) with a VB, VBA, or VBScript subroutine or function can be a bit confusing. We will first examine how to set up the code structure for a subroutine and function, and then we will look at how to call that subroutine or function.

Subroutine Code Structure
If a subroutine does not receive any arguments, then you do not use any parentheses when declaring the subroutine. Note the required use of the Sub and End Sub statements which define the start and finish of the subroutine code.

Sub MySubroutine
    'place your code here
End Sub

However, if a subroutine does receive arguments, then you must use parentheses in its declaration. If there is more than one argument, you must separate the arguments with commas.

Sub MySubroutine(intUsageFee, intTimeInHours, strCompanyName)
    'place your code here
End Sub

Function Code Structure
As with subroutines, if a function does not receive any arguments, then you do not use any parentheses in the function declaration. Note the required use of the Function and End Function statements which define the start and finish of the function code.

Function MyFunction
    'place your code here
End Function

However, if a function does receive arguments, then you must enclose its argument list in parentheses when declaring the function. If there is more than one argument, you must separate the arguments with commas.

Function MyFunction(intUsageFee, intTimeInHours, strCompanyName)
    'place your code here
End Function

Calling the Subroutine
There are two possible ways to call a subroutine. You may either call the subroutine directly by name only, or you may call it by using the VBScript Call statement.

Calling a Subroutine by Name
If a subroutine does not pass any arguments, then you do not use any parentheses.

MySubroutine

Even if a subroutine has arguments, you still do not use parentheses. If there is more than one argument, you must separate the arguments with commas. If you enclose the argument list in parentheses when attempting to call a subroutine that takes more than one argument, you will receive the runtime error "Cannot use parentheses when calling a Sub".

MySubroutine intUsageFee, intTimeInHours, "DevGuru"

Using the VBScript Call Statement to Call a Subroutine
The use of Call statement is optional when you wish to call a subroutine. The purpose of the Call statement when used with a Sub is to allow you to enclose the argument list in parentheses. However, if a subroutine does not pass any arguments, then you still should not use parentheses when calling a Sub using the Call statement.

Call MySubroutine

If a subroutine has arguments, you must use parentheses when using the Call statement. If there is more than one argument, you must separate the arguments with commas.

Call MySubroutine(intUsageFee, intTimeInHours, "DevGuru")

Calling the Function
There are two possible ways to call a function. You may either call the function directly, by name only, or you may call it by using the VBScript Call statement.

Calling a Function by Name
When calling a function directly by name and when there is no assignment to a returned value, all of the following are legal syntax:

MyFunction
MyFunction()
MyFunction intUsageFee, intTimeInHours, "DevGuru"

If you want a returned value, you can assign the function to a variable. Note that if there is one or more arguments, you must use the parentheses.

returnval = MyFunction
returnval = MyFunction()
returnval = MyFunction(intUsageFee, intTimeInHours, "DevGuru")

Using the Call Statement
If a function has arguments, you must use parentheses when using the Call statement. If there is more than one argument, you must separate the arguments with commas. There is no returned value when using Call.

Call MyFunction(intUsageFee, intTimeInHours, "DevGuru")