I think what you would have to do hear is Convert Expression to Keyframes. The problem is that you'll get a keyframe for every frame. Look under Animation Menu> Keyframe Assistants> Convert Expression to Keyframes.
You might try to look at your Motion Graph and delete all but a few spread out keyframes. That would allow you to then use the bezier curves on those keyframes.
It's kind of tedious, but it works.
Something you might try (this depends on your interest in Nulls) is to use the position of a Null to do fine adjustments on the position of the particle emitter.
Good Luck!
Trent
Trent Armstrong - Creative Cow Leader
http://www.dallasaeug.com
