How can I get my dog to stop spaying?

I have a two year old Chihuahua mix. He has a heart murmur and so the vet will not neuter him. He is house-trained, not aggressive or even yappy which is pretty good for a Chihuahua. We have another dog, and female Chihuahua mix who has been spayed. They are basically the same age and we have had them both since they were young puppies, They get along well together and until about 6 months ago there was no problem. I am basically looking for something to deter this behavior. Thanks!

What do you mean by spaying??

if ur dog is spraying? then u should get him neutered. the vet really has no right to disagree. Vets should agree to neuter him it will make him more calmed and patient after the neuter. If the vet is not willing then ask for a reason, it may be a condition of the dogs but if not change vets.

Um, did you mean spraying as in marking? If so, it will be hard since you can't neuter him. Maybe talk to a trainer that specializes in this kind of thing.