请问这句话的意思: “Not if I can help it, son .”

请问这句话的意思: “Not if I can help it, son .” Aren't you going to shoot it?" asked the boy. "Not now, son ." "Are you going to let it go?" “Not if I can help it, son .” "Then why don't you shoot it?" "It just doesn't seem fair." 1. 请问这句话的意思: “Not if I can help it, son .”2. 这应该是省略的,那么完整的句子是什么呢?