The discipline for house training wrecks should be administered to the humans involved, not the pup. If you catch him in the act, just say something like "oops" and pick him up and take him outside. Right then. Personally, I've not had much luck intercepting (my fault not the pups). But frequent outside trips "putting a name on it" and praising like they just found your lost gold watch seems to work. My pup has figured out what "whizz" means and what "poop" means. Or at least what activity in response to those words gets a lot of praise.