With your typical external midi fader box like the Peavey PC-1600(x) or an Encore Knobby, you can record MIXER setting during real-time record. Just setup your knobs/sliders on the midi control box to transmit these midi sysex strings:
F0 47 00 44 45 (Event Type) (Pad Number) (Value) F7
There are four types of events.
01 STEREO LEVEL
02 STEREO PAN
03 FXsend LEVEL
05 INDIV LEVEL
Pad numbers A01 ~ D16 correspond to 00 ~ 3F.
Value can be set between the range 00 ~ 64
Be sure to program the box not to exceed 64 or else midi note data gets erased! If you have pushbutton you could also program mutes with them by using a VALUE = 0 for the LEVEL settings. Unfortunately,this only works during real-time record (or step-entry) and not during real-time play. I had hoped it would. Ah, something for the wishlist.