I recommend to equip the Buffer objects with an user defined attribute lastExitTime of type time.
The rear triggered exit control does not need a move instruction. The MU is moved at this moment.
The code of the exit control is
?.lastExitTime := EventController.simTime
This value can be displayed as a Display Panel, which can be defined via the context menu of the Buffer object.
You can do it in the class of the buffers: