Well, in spite of the fact that there are cats living under the barn, and now the neighbours are feeding them, I am still getting access to the field. We have worked out a compromise. We enter the field on leash. Instead of passing the barn at the end of our walk, we walk past it first. We stay on leash. Once we get past the barn (and I saw a different cat their a few nights ago), we get to be off leash.