My horse won't let me catch him?

Well, this horse DOES ociate catching him with work. You are cueing this horse even if you don't realize it and he has learned when you mean to only give him treats and when you mean to work him. Try doing exactly as you would do if you were going to work him. Catch him, halter him, groom him, give him tons of treats then turn him loose. It'll confuse him, but soon he might be willing to risk being caught if it doesn't mean work all the time.