I don't know if it's possible since Side Chain volume is controlled by another track.
Right on the money, Norman.
The UNI COMP DSP algorithm has four parameters for side chain: on/off, EQ Q, EQ freq, and EG gain. it is the same algorithm as Montage/MODX, except Montage/MODX provide a way to connect a part to the side chain input. It's in the Montage/MODX user interface and effects engine.
The Genos (PSR, Tyros) legacy XG effects engine doesn't have such a feature, i.e., using a part to control a DSP effect parameter.
This is another item for the Genos development team.
All the best -- pj