Reply to Traktor with expression pedal?

Hello djtt members, got another question for you all.

Is there anyway I can use an expression pedal to control a knob in a fx rack a kontrol s4 and foot pedal? If not, how can I use my m audio venoms pedal input to control it?

I want to use an expression pedal to control the third knob in my fx rack. Hardware wise I have a kontrol s4 with a foot pedal input on the back of it. Can this input utilise an expression pedal or just a foot switch?

I also have a m audio venom connected via a midi cable to the s4's input. It has a dedicated expression pedal jack. How would I go about routing the midi from the foot switch into traktor? I tried to do it in the kontrol manager with the learn feature but traktor wasn't picking up anything.