keyboard shortcut for scrolling

I know i can do this w/the mouse w/wheel but I need the exact keyboard shortcut to assign to my wacom tablet.
OK, I want to do the horizontal scrolling on the wacom intuos 4 but it only has the vertical scroll ring. I can click on "SHIFT" while scroll to get the horizontal scroll but I want to just do this in 1 move. SO, what's the internal keyboard shortcut that mac osx using to assign the scroll button?
example: if it's like "command optionLMB" for scrolling then I can assign "shift command+optionLMB" to the wacom's ring to get the horizontal scroll.

so anyone has light on this?

thanks
J