Is there no way in OS X to change what the extra mouse buttons, found on any modern day mouse, do? I know I can buy USB Overdrive or Steermouse, but it seems ridiculous to have to spend $20 to redefine some mouse buttons. I have a Logitech MX518 that I much prefer over the wireless MightyMouse that came with my Mac Pro. I can't for the life of me figure out how to change the mouse buttons. I did a search through the forums already and it seems the only answer is to buy some additional piece of software. That's most unfortunate.