Perhaps make the Listener the Starting State. Then based on say an OnTrigger event, your Listener would fire off the Level Checker. At this point you'd have 2 transitions to different states. If your player character met the required condition, onto the LoadLevel. If not then back to the listener for another try.
So lets say for instance, your 'unlock' condition was contingent on your character's color being Blue. If your character walked into the Listener/onTrigger (while he was say...red), the Level Checker would fire and then test for whether his color was red or blue. Since he was red it would fire off 'is locked' event and not LoadLevel event. Your character would still need to figure out how to become 'blue'. Maybe some interaction or other object in the scene. If he were blue, the Level Checker would fire the Is unlocked event, and your LoadLevel would fire.
hope that helps.
B.