Native Instruments Razor in Reaktor 5 Player

I bought Razor this morning to mess around with, and I'm using my MPK Mini MIDI keyboard to play with it. I found that the 'mod wheel' was automatically assigned to one of the knobs on the MPK mini, and I could use the MIDI Learn command in Reaktor Player to assign other on-screen knobs to the controls on the MPK - and I want to assign the pitch bend command, but I don't believe it's an on screen control (like the mod wheel) so I'm not really sure how to assign it? Couldn't find anything in the manual about assigning MIDI controls so I'm not sure if it's even possible in Reaktor 5 Player...