Elektron Musical Instruments

Hey all!
I can't quite get this feature to work.  I forget the actual name (I'm
not in front of the MnM right now), but it's the option of choosing
which track sequence will trig a specific track.  Whenever I set this to
something other than "---" (which is just the chosen track itself),
nothing different happens.

Am I doing something wrong?  Or is my understanding of this incorrect?
That is, as I understand it, this choice allows you to choose which
sequence will trig which track.  For example, choosing track 4 to
sequence track 2 will cause the sequence programmed into track 4 to
actually sequence track 2 (in addition to track 4, if assigned properly).

Thanks in advance for any help!
Joe