Thanks for the clarification. For some reason, I was thinking you wanted to connect another footswitch directly to the pedal, obviously not at all what you have or wanted to do.
If Ron's suggestion doesn't work for what you want, look at the pedals midi implementation chart and see if there's a CC number that correlates with the function you're after. Then assign a CC number to the 2nd button on your footswitch. Bank up/down should be Device PC+/Device PC- though.