Player attacks a certain type of building trigger

I'm trying to make a trigger where if a player attacks a certain type of structure (not a specific structure pre-placed on the map) it checks to see what kind of unit attacked the tower. Then something special happens if it was the correct type of unit. Can anybody help me with the event here?

EDIT - I've gotten the trigger to work somewhat so far. If I click on the building type it displays a message. But how do I make it so if the order being issued is only an attack order?

EDIT2 - Nevermind I've figured this out on my own already. Thanks! LOL. :P