Not sure that I understand. But, if I do, you are looking for some kind of MIDI message to notify you of knob values being updated on loading a preset.
There is none – and probably unlikely to be so, as the work involved in doing this would slow the unit down, for something that would benefit very few guitarists.
What you could do, since you know when the preset is changed, is to download the new preset and read the knob values. This will require a sysex and C programming.
