It'd be better to ask this question in the Public.Mac.Office.Powerpoint section
of the newsgroup; it's not really obvious from the name, but this is mostly a
Windows PPT oriented group. For "How do I do this in PPT" type questions, it
doesn't always matter which group you post to but since Keynote is only
available on Mac, you'll get better answers by talking to our buddies over on
the Mac side 'o the fence.