I cannot find anything in the CK that seems relevant, except perhaps this, but I don't know how to use it. As usual, the CK utterly fails to define it's terms.
What the hell is a "volume"? Let alone a "Trigger Volume"?
OnTriggerEnter - ObjectReference
Member of: ObjectReference Script (Papyrus)
Event called when the object reference is a trigger volume and has been entered.
Syntax
Event OnTriggerEnter(ObjectReference akActionRef)
Parameters
akActionRef: The ObjectReference that entered the volume.
Examples
Event OnTriggerEnter(ObjectReference akActionRef)
Debug.Trace(akActionRef + " just entered us!")
EndEvent
Notes
This event can be received out of order with OnTriggerLeave, so it's ideal to keep a count instead of a simple true/false value for when things are inside the trigger.
See Also
ObjectReference Script
OnTrigger - ObjectReference
OnTriggerLeave - ObjectReference
GetTriggerObjectCount - ObjectReference
~.~