Pay back for training costs

Q. Training in our field is pretty specialized and expensive. We don’t mind investing in our employees, but want to make sure that we get the benefit of the training. We have a requirement that newly trained employees must continue to work for us for at least six months following their training, or they are required to pay back the company. Our problem is how to make sure they pay it. Can we deduct it from their last paycheck?—D.B.