Ah yes, I meant ApplyEffectToObject and ApplyEffectAtLocation, as they are in NWN2. I was working from memory and sometimes the details are off.
ApplyEffectAtLocation(int nDurationType, effect eEffect, location lLocation, float fDuration=0.0f);
ApplyEffectToObject(int nDurationType, effect eEffect, object oTarget, float fDuration=0.0f);
ApplyEffectAtLocation actually creates an AoE object that has its own tag and can be selected with GetObjectByTag or any other object functions, but if DA:O doesn't include it, then it's still fine as long as there are invisible and intangible objects that can accept effects (waypoints don't seem to work, so it has to be a placeable.
If you're creating a trap, then you should be able to apply a script directly to that instead of making an AoE that does it, but then you need to deal with removing all of the trap-related material like characters being able to detect it, disarm it, etc.
If you apply the AoE to an invisible placeable (in NWN2, we have such a placeable called an ipoint -- maybe you do, too) instead of to a trap, then you don't have to deal with that, and the AoE handles the script On Enter, doing only what you tell it to. In that case you would also want to destroy the invisible placeable (taking the effect along with it) after you're done.