I have a Function that uses a  Name( ) as String component. I want to
call this function but change the string name as desired.

eg

Dim  Test1( ) as String
Dim   Test2 ( ) as String

Function DoThis(Name( ) as String)

.....
y= Name(i)

End Sub

When I call the function with DoThis(Test1) or DoThis(Test1( ) ) I get a
mismatch error

Appreciate if somebody what silly mistake I'm making

Thanks

could be that your Function is getting confused.  I think the word "Name"
may be reserved by Excel/VBA.  For example,

Name OldName As NewName    ' Rename file.

Try changing the name of your variables/parameters to something else.

Regards

Trevor