Keyboard shortcut for "Tile right" and "Tile left" buttons

Hi,

I'm using SolidWorks 2012 with dual screens and I like the "tile right" and "tile left" feature that comes with this new version, however I want to be able to assign each of these to a keyboard short cut (specifically "Shift+1" and "Shift+2"). I haven't been able to find the buttons in the "customize" dialog window. Am I just missing it, or is this not possible?

Thanks for any help!

SolidworksUser Interface