Well
For your reply xxconanxxx your trigger is right but you need a condition.
Event-Unit enters region
Condition-Owner of trggering unit equal to player12(brown) or w.e
Action-Order unit to attack move to *region*
In your reply xxconanxxx your trigger would make any unit attack move to the regiob.
In mine it only makes player12 brown attack move to the region.
Hope that helped you.