[Jimmy Cao]

Unfortunately, I am not familiar with which pins do what on a mouse. You should probobly either contact a manufacturer or dissassemble an old one to figure out what goes where. You will need to definately wire up the power (prob 5 volts) and ground. There should be 2 digital lines for the encoders, and (at least) 2 digital lines for the clicks (maybe one more for the wheel). You will not need to use the clicks or the wheel, so do not wire them.

To test, check for continuity or resistance through the mouse as you move it back and forth, and see if the line ever reads high.

It wont be easy. I know (at least) one team used a mouse, so they may know better than I do.