I've come up with a way to subclass the focused control on the fly and watch for WM_XBUTTONUP messages.
This seems to work fine with my microsoft mouse.
However this method functions differently than the previous, the previous design looked for Forward/backward messages allowing the user to assign them to any mouse button.
This new code is button specific, the left X button is backwards and the right X button is forwards.
Please email me at
support@flashfxp.com and I will provide you with a test copy.