Yes, it's possible to use any number of mice... You won't get 2 mouse pointers in Windows (it's not prepared to handle more than 1 mouse), but from an application you can get the info about the mice and handle them. (There is a special build for MAME which handles 4 mice as input devices...)
On
this page you'll find loads of info (including source code) about multiple mice handling...
Have fun...
