I am afraid it won't be possible with regular signals as they are constants - no way to specify different values for different signals for same definition but enclosed within multi instance activity/subprocess.
I would attempt to do it via domain specific activity that register itself as event listener and then each instance of that activity would be listening on slightly different signal name. Then remodel the process to use parallel gateway to split the logic and when signal arrives that should move the subprocess flow to terminate end event in the subprocess to cancel user task when exiting from subprocess.
I wish this is impossible.
Anyway, thanks for that information, I'll try diffrent solution.
actually I believe it is possible just requires some development but should be doable.