If arguments of a method are enclosed in parenthesis, you must use the Call statement to transfer control to a method.
If you omit the Call keyword, you also must omit the parentheses the list of arguments is enclosed in. So, your code should be either as follows:
or as follows:
Call aqFileSystem.CopyFile("C:\tc_test.txt", "D:\tc_test.txt")
Please refer to the following MSDN article for more information:
aqFileSystem.CopyFile "C:\tc_test.txt", "D:\tc_test.txt"