Well, yeah, or make it in accessible to them. *Edit* Getting rid of it would make things easier, I'm guessing, but if you want to keep it around, you can make the transition, just is a bit tougher, and requires a bit of patience.
What we do, is that when the birds are done young bird racing we start the process of trying to get them to trap in the old bird loft. The first few times they will sit out all day trying to get into the young bird loft and then at the end of the day we will open up the young bird so they can trap in. Run them through the bobs of the old bird loft, and (a settling cage will also help this immensely) they should start to figure it out. If they frustrate you enough, you can leave them out over night and they will start to figure things out in a hurry. Just hopefully you have enough that if you lose one or two to hawks, that it won't hurt you too bad.