In VBScript, functions should return a value. You cannot call a function without setting the returned value to a variable (unless you use "Call"). If you do not intend to use the returned value, then you should consider refactoring your code.
The best practice syntax for calling functions and subroutines is as follows. I personally avoid using "Call" as much as possible.
On another note, the type of a variable is Empty until it is initialized. You may experiment with "VarType()" to determine if "Call" has any effect of the type of a variable.
Function returnAValue(ByVal blValue1, ByVal blValue2)
returnAValue = blValue1
Sub noReturnValue(ByVal blValue1, ByVal blValue2)
' Do something
blReturnedVal = returnAValue(True, False) ' Call a function with parameters in parenthesis
noReturnValue True, False ' Call a subroutine without parenthesis