That's tricky.
What you need is an event called "Trigger Zone", which has been causing trouble to people in the past as well. I'm not sure whether you need any updates or something to use it, and I don't have a JCS here to check, but I'll try to help anyways:
As far as I remember, there are three fields to fill out for that event. One is the Trigger ID, which works just the same way as the Trigger Crate. It will trigger any Event Scenery with the same ID number.
Then there is a field that, if 1'd, makes the trigger a switch that can be turned off and on, but you apparently don't need that.
As for the last one, I dunno.
Also, I believe that the ID number has to be higher than 0, otherwise it won't work.

I hope I recalled correctly here.