Documentation
Call
is an optional keyword, but the one caveat is that if you use it you must include the parentheses around the arguments, but if you omit it you must not include the parentheses.
Quote from MSDN:
You are not required to use the Call keyword when calling a procedure.
However, if you use the Call keyword to call a procedure that requires arguments, argumentlist must be enclosed in parentheses. If you omit the Call keyword, you also must omit the parentheses around argumentlist. If you use either Call syntax to call any intrinsic or user-defined function, the function's return value is discarded.
To pass a whole array to a procedure, use the array name followed by empty parentheses.
Link: https://msdn.microsoft.com/en-us/library/office/gg251710.aspx
In Practice
This means that the following syntaxes are allowed:
Call abc("aaa")
Call abc("aaa", 2)
abc "aaa", 2
abc("aaa") ' <- Parantheses here do not create an argument list
abc(((("aaa")))) ' <- Parantheses here do not create an argument list
The following syntaxes are not allowed:
Call abc "aaa", 2
abc("aaa", 2) ' <- Parantheses here create an argument list
Function Return Values
This doesn't take effect when using a function to get a return value, for example if you were to do the following you need parentheses:
Function abc(a As String, Optional iCol As Long = 3)
abc = iCol
End Function
'## IMMEDIATE WINDOW ##
?abc("aaa", 2) 'this works
?abc "aaa, 2 'this will not work
?Call abc "aaa", 2 'this will not work
?Call abc("aaa", 2) 'this will not work
If you are using Call
on a Function
then consider changing it to a Sub
instead, functions are meant to return a value as in the cases above.