I had similar problem like you (I posted it here: viewtopic.php?f=49&t=18464
). I solved it with program BTNX ( viewtopic.php?f=49&t=18464
). You can try it, it's great!!!
Only problem for me now is that when I press SEARCH button on my Logitech MX620, Search File is opening by default. So even when I reconfigure it with BNTX pressing on that button cause two actions: the one I defined in BTNX and another action is default action (opening Search File). I tried to disable default action, but I couldn't make it