Using a synth knob as a fader

Hi guys –
Anyhow ever use a synth knob as a fader? Perhaps it’s harder than I thought, because I can’t figure it out. I’d like to be able to assign, say, my Sub37’s big old filter knob to act as the controller for an automation lane. Possible? THanks!

Yes, if it sends MIDI

I’ve been able to assign midi cc to my knob as well, so yes!