ok dude, couple of things:
1. once the creeps spawn, does the trigger pick all the units and order them to move? if so, the next trigger, where they are moving to, is it correctly triggering, so that when a unit enters that region it sends them to correct location and not the other region??
2. if not ^ is your trigger: Action - Create blah units facing blah blah... or is it sumthing else? coz if its that trigger, they should not move unless they are triggered to, or they are being attacked.. forcing them to move away.
im just guessing ur trying to do some kind of maul type gameplay? not sure.. lol
check those, if they dont solve, describe a little better of your problem.