1) Place an OPFOR unit with a "Guard" waypoint.
2) Place a BLUFOR unit as player somewhere out of sight of the OPFOR unit and his waypoint.
3) Run a sqf file containing the following scrip from init.sqf
[CODE]
_trg=createTrigger["EmptyDetector",getPos player];
_trg setTriggerArea[5,5,0,false];
_trg setTriggerActivation["WEST","PRESENT",false];
_trg setTriggerType "EAST G";
_trg setTriggerStatements["this", "hint 'trigger is on'", "hint 'trigger is off'"]; [/CODE]