Mainstage 3 Volume boost for guitar solo

Good day. I am a complete MIDI novice so please keep answers as simple as possible. I am programming an Xtone Pro device to work with Mainstage 3. Have got most of what I want done but was wanting to assign one of the controls on the pedal to do a volume increase of about 10% when pressed then go back when pressed again. The idea is to hit it for a volume boost during guitar solo, then turn it off. Any ideas how to do this are welcomed.