To use the F9 and F10 keys to control Exposé, you need to do one of two things:
- Press the fn key with F9 and/or F10
- Go to System Preferences > Keyboard & Mouse > Keyboard and check the box 'Use F1-F12 keys to control software features' and use the fn key with F9 and/or F10 to control the keyboard backlighting. If you check that box, then Exposé will behave in the same way it does on your iMac wrt your mouse buttons.
