You can consider trying one of those collers that shock the dog when it barks...it's kind of mean but i think it works. My dog is exactly the same way, i get him to sit before i put him in the backyard and I tell him "okay" but when he goes outside, he goes crazy. He runs all around the yard barking at everything, cars, the neighbours, whatever the case happens to be. We just got the shock coller but i think it was out of batteries or something. But our neighbour said he had a jack russel that was like that and the coller worked for his dog. Hope this helps!