Open parentheses should not have any space before them in function, sub, and property declarations or calls.

Anti-pattern

' The space after Foo is unnecessary
Function Foo (Bar)
End Function

Best practice

Function Foo(Bar)
End Function

Exceptions

This rule is not universal and only applies in a few contexts. Whitespace must exist before parenthesised expressions and in declare statements.

Public Declare Foo "Bar" (Baz)
Function Foo(Bar)
    If (Bar > 6) Then
        Foo = 3 * (1 + 2)
    End If
End Function