I need trigger help!!!!

below is a raw model of my map.
the (!?) is a point where im having trouble. The (0) is not important. The (\ and |) are the suggested routes.I have made triggers so that the creeps will attack-move to the !? location, BUT from there on they won't move to the enemys base, since I can't make any working triggers from there on. If you can't make any sense of the(shitty)help picture, my map is somewhat like DOTA, only much, much larger.
Im asking help from anyone just help me.

Base------------------!?
|000\0000000000000|
|0000\000000000000|
|0000000\0000000000|
|00000000000\000000|
|000000000000000\000|
!?---------------------base

Events: unit enters rect (at the '?')
conditions: (unit belongs to player X)
Actions: unit - order unit to move to 'base'

THNX