Hi Stargate Fan,
One way to do it:
Open the Object browser (F2), look up your macro.
Then right-click on it, choose "Properties..." from the context menu that
appears, and edit the Description.
In Word 2003, the description doesn't show in "Customize..., Commands tab"
though (probably a bug).
It does show up in the keyboard customization dialog and "Tools > Macro >
Macros".
Regards,
Klaus