Scripting with the RPG

Hello everyone!

I'm trying to do some very base scripting using the RPG in HL2:Ep2, and I've run into a snag. How do you reference the RPG rounds in inputs/outputs?

Currently, I'm using a trigger_rpgfire block to try and cause the rocket to explode 2 seconds after being fired, but the !activator is the player, not the rocket itself.

Eventually, I want to essentially have a laser-defense system, where a laser beam appears from one point and ends at the flying rocket, causing the rocket to explode. In any event, I still don't know how to refer to the rocket. Can anyone provide any pointers? Thanks guys.