Customizing Function Key Row

Alright - I have a very random question that I'm pretty sure isn't possible, but hey I thought I'd ask anyways. Is there anyway to fully customize the row of function keys on my Powerbook, for having them do what I want them to do? For example, with the Fn key enabled in OSX, I can change the volume by just hitting the keys, without having to hit the Fn key, which I like. But when the Fn key is enabled, I can't use Expose without pressing it first. I'd like to be able to kind of apply the Fn key to half the function row - I want to be able to change the volume by just pressing F3 to F5, and likewise, I'd like to be able to use Expose by just hitting F9 thru F11 - all at the same time. Is this remotely possible?