Found this tool today. It's very useful.

http://www.highrez.co.uk/downloads/XMouseButtonControl.htm

Had a request from a drafter/designer to zoom into his CAD session using some spare mouse buttons on his MS Intellimouse. I was amazed he was using such a comparatively primitive tool, but apparently that's what they issue...

So, first I tried the keymappings for the CAD which was a simple + or - char, to zoom and mapped it to the mouse buttons using X-mouse. This didn't produce the desired result, response in repeat mode was jumpy and seemed to be snapping to wrong areas without any mouse movement present. The CAD program seemed to refresh every layer in the window in slo-mo further grinding things down.

 I decided to use another option... X-Mouse supports {MWUP} {MWDN} (mouse-wheel UP/DOWN) when the button was held down. I had noticed that this did not have the same effect in the CAD program and was much smoother. This was perfect, added in a 50ms delay or so, and away it went, worked like a charm!

This program is PayPal donation-ware and I highly recommend it (at least under 32-bit XP SP2 and Windows 7 Pro).

MicroSoft IntelliPoint 8.2 was tried first, and while it worked, did not have anywhere near the flexibility of X-mouse. I ended up uninstalling it, whereupon it cunningly changed the double-click to an unusable state (far too high) for no apparent reason. I set this in control panel again and all was well once more.

The next little challenge was to get similar functionality on another machine (Win7 Pro) with a basic HP 2-button mouse, this was also achieved by setting a held Hotkey (CTRL) to switch to Layer2 in X-Mouse and defined similar button mappings. The machine was a powerful HP Z210 and this functioned very nicely indeed. I only introduced a 20ms delay, this was too fast for my personal liking, but the user was very happy with it.