I have this script that works nicely for my needs. Basically what it does is, if the player steps into the area, it applies slowed and bleeding to them unless they have the desert gear.
IF
CharacterEnteredTrigger(_Player,TRIGGERGUID_DC_AllDesertAuraQuest_f74d0900-e3dd-4fa2-ac5e-28e2a20b1095)
AND
IsTagged(_Player,"DC_HasDesertGear",0)
THEN
ApplyStatus(_Player,"SLOWED",-1.0,1);
ApplyStatus(_Player,"BLEEDING",-1.0,1);
DisplayText(_Player,"Ouch! These winds are dreadful! The sand rips at my skin!");
That checks if the player don't have 'DC_HasDesertGear' tag. (_Player,"TAG",0=Dont have, 1=have tag)
Perhaps you can derive something from that?
Example:
IF
GameStarted("YourLevel",0)
AND
IsTagged(_Player,"NotStarted",0)
THEN
YourScript(_Player,"CoolStuff",1);
SetTag(_Player,"NotStarted");