Putting a shock collar on an aggressive dog may only make the problem worse. The problem is a dog is barking or aggressive towards an object or person or other animal and receives a shock he will soon associate the shock with the other entity and then assume that the entity is causing the shock making him more aggressive. To be honest this situation requires a twofold solution. First off you need to get a physical barrier, a real fence. Secondly you need to get Professional Dog training and behavior modification.

If you can't handle a dog you shouldn't have gotten one. Bring him to a non-kill shelter to be adopted by someone that is prepared to handle any sort of temperament a dog can possibly have.