Ok I want to call a script when my NPC enters a specific area (a cage). I foundhttp://cs.elderscrolls.com/constwiki/index.php/OnTrigger on the script part, which I can understand. However, I don't see anything about how to create the zone? I want to add a zone where the NPC enters the cage and then I run my script. I don't know how to define this zone in the CS though. Is it an activator? Any help much appreciated.

All trigger zones in the CS are from two meshes.
Check TrigZoneACTOR01 and 02 under Activators.
Duplicate one of them, scale it and position on your cage.

Awesome thanks!