trigger help

i want something to be activated when a unit from each player moves into a region. Im having trouble checking if that player is even playing so the trigger wont need that players unit to activate.

maybe

E = Event
C = Condition
A = Action

Trigger 1
--------------

E: Unit enters region
C: Owner of triggering unit = Bleh
A: Set VAR +1
A: Run trigger 3 (checking conditions)
A: Turn off this trigger
A: Turn on trigger 2

Tigger 3
-----------------
E: (whatever or blank here)
C: If VAR =or greater then 4 (or X)
A: Do (whatever u want)

Tigger 2 (Initaly Off)
--------------------
E: Unit Leaves Region
C: Owner of triggering unit = Bleh
A: Set VAR -1
A: Turn off this trigger
A: Turn on trigger 1

now u need to copy trigger 1+3 for each player.... Hope this helps