You can set the Start script for the trigger to "appearifactivate.fpi". Then you can do either of the following:
Switch
1. Go into the Switch properties and put the name of the trigger in the IfUsed field. When the player activates the switch, it will activate the IfUsed field (your trigger).
OR
If you want the switch to open a door AND activate your trigger you can:
1. Go into the switch properties and put the name of the door in the IfUsed field. When the player activates the switch, the door is activated.
2. In the switch script, you can use the "settargetname=yourtriggername" and "activatetarget=1" to activate it. This is how you can activate multiple items with just one script.
Twitter: @NFoxMedia