Middle-click emulation under windows?

[Cerb]

Is there any program for Windows (2000) that will do a X style middle click emulation (leftclick + rightlick within a small time period = middle click)? I really like the feel of Kensington's Orbit Optical, but I also need to use a middle button. Its software does not appear to have such an option, and I can't find any program that does it, but it seems like there should be some out there.