Greetings,
I'm sure a quick search of the forum would reveal the answer, but still...
Put a "MOVE" waypoint before the load waypoint. put it some distance away, and sinchronise that to your trigger. Put a "GET IN" waypoint for the troops and sinchronise with the "load" waypoint.
The chopper will go to the move wp, and wait there for the trigger to be activated. Then it will go to the load wp, and the troops will get in. After that, it will continue on the wp path.
Hope it helps,
-Supreme Commander PsyWarrior
-Psychic Productions