Logitech MX510 Mouse Config question

Hey, I am trying to configure a Logitech MX510 Mouse with my PowerBook G4. Using the Logitech config utility I can assign actions to the extra buttons on the mouse. I want to assign Fn-F9 (the Exposé thing that shows all your different things at once) but it doesn't accept that keystroke, I think because the powerbook initially has F9 as 'dim keyboard backlight' or whatever and it seems to bypass the regular function. I have to press Fn-F9 to do the Show All Programs thing, but it doesn't read that in the config utility.

A solution would be very helpful. I am looking for the mouse configuration files, but I am new to Mac OS X so I'm not sure which directory to look in, although I have used the terminal to browse thru the dirs a little bit.

Thanks

Scott