You could have downloaded iTunesMouseRemote 0.1 for Mac from our application library for free. This free software for Mac OS X is a product of Robin Hamilton-Pennell. The application lies within Audio & Video Tools, more precisely General.
From the developer:
iTunesMouseRemote turns your shiny three-button mouse into a remote control for iTunes. You can activate it by selecting the "iTunesMouseRemote" option from the script menu in iTunes, and press Esc to deactivate it. Basically, it makes your scroll wheel a play/pause button and volume knob, and your left and right buttons into next/previous track buttons. It's somewhat of a proof-of-concept at this point.