My Jack Russell terrier was doing the same thing recently. When he wanted to come in, he would reach through the hole in the screen door and tap his nails on the tile floor. I would hear the sound and hurry over to open the door.
This went on for a couple of weeks and I began to get annoyed and feel like my dog's servant when I had to drop what I was doing to open the door.
Then one day, I just stopped answering the dog's knocks at the door.
It was an, ominous gloomy day outside and it was about to rain. Then the dog heard a clap of thunder, and I imagine that he said to himself "Screw this, I give up." because then I saw him push the screen door open with his nose and come in the house.
