I highly suggest you get a decent gaming mouse that comes with this feature. I have owned several, low to high end and a decent one can be purchased for under $30 bucks. The link is one of the mice I use on my four gaming PC's lol. It is my favorite and was the cheapest! ($24)
But as with any purchase do your own research. My overall point is, once I started using mice that came with software with the ability to program each button, I can never go back for the very reason you are frustrated.
V/R Fawlkon
Game on!
