How do you change key bindings for a MAC?

I have been playing Batman: Arkham Asylum for a few hours now, but i am having some trouble with the controles. Some moves require and left and right mouse button to be pressed simultaneously, and some moves require a middle mouse click. The mac (without an attachable mouse) simply cannot perform such functions. Is there a way to change the key bindings for the mac to make playing a lot easier??? Any support would be greatly appreciated. :) Take care.