Unit Group dies, turn on trigger

Ok, what im trying to accomplish here is...

1. you cross a bridge and you see 3 ogres.
2. you walk past the ogres, up to a closed gate.
3. you cannot get in...
4. you turn around and kill all 3 ogres.
5. a region now appears allowing the gate to open if you step on that region.

well...what i need no know is, how do i put those 3 ogres into a variable that make it so that only if all 3 ogres are killed, will the region appear allowing me to trigger the gate to open.

Thankyou in advance for the help! =)

Here

Make a unit group varible. Set varible (what you called your variable)"Ogregroup" = units in region (make a region accros the 3 ogres, and then select the region) "region001"

Make trigger:

ACION: time every 1 seconds of game time

CONDTITION: bolean, unit group, all units of "ogregroup" are dead agual to true

EVENT: whatever you want (dont forget to turn of this trigger, using; "trigger- turn of this trigger")

Hope thats it

Dont ever check anytihing every 1 second unless your making a lag map. Espeically a trigger as simple as you need.

Event:
Unit owned by player (nutral hostile) dies
Condition:
all units in unit group are dead
Event:
Turn on trigger that opens door

It worked just like i wanted it to! thankyou so much! =))