Reply to USB Numpad as help-deck

I am in the process of buying and mapping a USB numpad as a help deck to complement my one Denon DN - SC 2000 and have stumbled upon an issue. How do I map it so that it uses the opposite deck of the one I have my Denon focused on?
I am asking that because I don't whant to use the numpad as my main second deck, I use the two-deck functionality of my Denon for that. However, there are times when I am doing a rather complex action which requires a second Play/Cue/Loop/Whatever button. What I want is for the numpad to automatically change the deck it is focused on to the one that I am cueing - going to air. Is it possible?

What do the "Deck Focus" options on Traktor Pro 2's mapping section do?

Thanks!