My dog

I'm not sure how much it costs and if you can afford it, but there's a training method called Invisible Fencing. I'm not even sure how it operates. However, I've heard that ground cayene pepper is a good thing to use to keep animals from crossing a border--either to enter or exit a yard. Just buy some and pour a line of it along the borders of your yard, and repeat as often as necessary so that your dog will associate discomfort with rushing off of your property.