Here is version 2
https://goo.gl/TXmtqH
several problems with it that could do with looking at including :
if you double click the left mouse the old group still is stepping through its loop so will flash onto the screen.
my method (event 6) of removing non group members could be more elegant.
I have a couple of ideas on how to fix these but I think for this demo it is good enough ?
over to you...