Setting back and forward as mouse buttons on a mac

Setting back and forward as mouse buttons on a mac

I'm a recent Mac convert, and reusing my good old Logitech MX500 mouse. One thing that I really miss is having Back and Forward set to the side buttons (buttons 4 and 5 I believe). Is there any way to do this? I'd like to have it work at an OS level (in Finder), but I'd settle for just having Safari work too.