I think you'll be better off creating an add-in. I don't know anyone who uses POTM -- or, if you're talking about an earlier version of PPT -- I don't know anybody who uses macros in POT files. Probably for exactly the reason you're running into. As you're findin out, unfortunately PowerPoint doesn't work like Word.
Here's bsic info on creating an add-in:
Create an ADD-IN with TOOLBARS that run macros
http://www.pptfaq.com/FAQ00031.htm