It is better to teach the "release" command rather than "stay" for this sort of problem. I had this exact same problem with Rylie:
http://www.yorkietalk.com/forums/gen...me-darter.html
I found that teaching her "release" was the best thing I ever did. You start out small only having them hold the sit/lay down for a little while, giving the release command, and rewarding with a treat. If they get up before you give the ok, you just correct them back into the sit/lay down. Eventually, they realize that only when you say "release" are they allowed to move. As they get better at it, you add distractions.
I can now jump around like a freak, say other random words, jump OVER her, pet her, throw toys/treats... you get the picture... and Rylie will NOT move until I give her the release command.
To get the door into the mix. We practiced the same way as the initial command. Put her in the sit/lay down and go and open the door a smidge. If she moves immediately shut the door (I also like to say "ah ah ah"), and correct her back into the sit/lay down. Go back to the door and open it a crack again and if she successfully stays, calmly shut the door and give her the "release" command and a reward. Progressively increase how wide you open the door.
We are now to the point where I can put her in the sit/lay down, open the door wide open, walk OUT the door and continue to hold it wide open and she WILL NOT move until I give her the release command. In fact, Rylie no longer even lunges for the door when we open it (even without putting her in the sit/lay down). She has just learned that she is not allowed out unless I pick her up and take her out there. I even pick her up to take her over the threshold to go on walks. That way, she never walks out the door herself and does not think that it is okay to do so.
Sorry for being so long winded. Read my old thread and what I posted here and see if it helps you at all. I hope it works for you!
My little Rylie is a reformed door darter and your little one can be too!
