I m having problems iwth using macros

1) I save a macro, say marco A on a file call test.xls, so
that everyone can use...

2) I saved the macro at "All Open Workbooks)

3) and then, I wanna use the macro A on another file call
anothertest.xls

4) I open both files, and try to run the macro A on
anothertest.xls;

5) however, the Run button is not enabled


Any suggestions? How do I make a macro that for any xls
files? or even another computer?

thx in advance.