Wacom Intuos pen mapping issue

So i'm trying to map one of my pen buttons to "step backward" in photoshop (ctrl + alt + z) and I have that keystroke set up and everything in the [Wacom Tablet Properties](http://imgur.com/wCC3gWJ) but for whatever reason, within Photoshop CS6, that button is still acting like right click. Does anyone have a clue as to how I can get this to work properly? It's driving me crazy.