I think you need a 3rd party program to do that. Maybe something like:-
I can't say how good or bad this program is, I've never used it. Just found on a google search -http://www.highrez.co.uk/downloads/XMouseButtonControl.htm
More info here - http://download.cnet.com/X-Mouse-Button-Control/3000-20432_4-75362562.html
Always AV check any downloaded program before installing - just to play safe.