I could have explained myself better
There is no
single command to eject the whole group, unfortunately. You can do this to eject
one unit:
unitname action ["eject", vehicle unitname]
unassignvehicle unitname (very important, this part)
Now you see why you need a script. But the whole thing is pretty easy. And like m21man says, just execute the script from the trigger. Just remember to make the trigger fairly large (at least the default 50 meters) because a trigger only checks itself every .5seconds. A fast moving plane/heli could potentially fly through trigger before it sets it off.
This is the classic eject script:
http://www.ofpec.com/includes/download2.php?id=114Your activation line of the trigger should be:
[groupname,vehicle groupname] exec "groupeject.sqs"