It depends on what you want to do with that trigger....
If you want to detect a detonation, activated by the player then sorry, i can't help you. Otherwise, if you want somebody to lay a satchel and then blow it after a certain time/a certain trigger is activated, then you have the possibility to have a certain unit to lay (_unit fire ["put","timebomb"]) the bomb at a given place (set by waipoint/domove command-plus-trigger) an later blow it when somebody enters the trigger area (_unit action ["touchoff"]).
Now you have an idea from mine. It might be useful...!