use a training collar,although not all will agree, but they are very effective, btw stopping a dog from chasing is the only real use i have found for them,i had the same problem with my dog,simply when the dog begins to chase use the stop command and if the dog does not respond to this, give a blast on the collar,i found after 4 or 5 times the dog wouldnt chase at all.it has also instilled a better response to the stop command altogether.atb