Linxcel KVM: use 3rd mouse button for hotkey switch?

I just purchased a Linxcel KVM, which is great (only one keyboard and mouse on the desktop now). The KVM works fine (except for the god-awful loud beep) but I'm looking to simplify my workspace even more (and give my shoulder a rest)- instead of putting down the mouse, reaching across the desk to press the KVM, then back to the mouse, it would be extremely efficient if I could just use the third mouse button, which I never use for anything else.

I looked at some of the free hotkey managers on download.com, but I'm assuming the hotkey programs won't work anyway, because the KVM intercepts the signal en route to the PC, so using a hotkey program to make the PC send keyboard commands to the OS wouldn't help...

Any ideas?

Thanks,
Keith

System 1: Single WinXP box
System2: Vista32 host, VMWare with clients including XP, Win98, and Ubuntu