Dell Mouse KM7120W Excel Assignable Action

Hi, 

I recently bought this keyboard and mouse. I work a lot in Excel and love the Excel function in the Peripheral Manager to use the mouse button to go to a "Previous Sheet", but there is no option to go to the "next sheet".

When I try to "Assign Keystroke" and use Ctrl + Shift + 3 (pg dn), it doesn't work.

It's a really cool feature but is pointless if I can't use it in the other direction.

Please help!!!

Kurt