DES, have you properly introduced your horse to the pen? By that I mean, lead him in to about the middle then lead him out. Place a very small pile of hay in there and again lead him in. Allow him to eat then lead him out. Repeat this a second time only you walk out and leave him alone to eat. Just as he's finishing, go in and lead him around the pen and leave and put him away. That's enough for one day. You've made it a pleasant experience, you've asked nothing of him, he's eaten. Let him mull on that. The 2nd day, double up on the hay and leave him alone but keep an eye on him. This time when you go back in, just stand there relaxed, taking a few deep breaths. Ask nothing of him, if he meanders around, fine, if not, fine. If he hangs with you step back a few steps. He may follow and that's good. Just turn and walk and stand by the rail. He's learning it's not such a bad place. The goal here is to get him to move without feeling threatened so your energy has to be such that he will walk. When about half way, ask him to turn the other way. Don't fret if you muddle your signals. He'll do what your body is telling him so try to remember what you did. There's no right or wrong as long as you don't blame the horse.