Sidechain summing

Is there a way of sidechaining channels individualy on their own channel strip rather than sending them all to a group as one? The reason being that I am on the verge of buying myself a tl audio fattrak summing mixer. If I use the only method i know how of sidechaining, which is sending all the things i want sidechained to the same group it will mean then sending that group to the fattrak as one thus using up a stereo summing pair. Hope that makes sense…