Oooh, boy, time to start from scratch with retraining about visitors!

You may need a friend or two to volunteer to help with this. Does he react at the sound of the doorbell or knock? When does the frenzy begin?

You'll have to keep him on a leash when you have visitors over for now. How do your visitors typically react? Do they act excited to see him? Really, it sounds like your best bet is to have him on a leash, and keep him focussed on you when the visitor comes. Don't make a fuss over him, or even the guest, just stay calm, but keep him calm, by reinforcing "sit," with the leash. Once you and the guests are seated, keep him next to you, still on the leash, so he cannot ignore commands.

If you have a willing friend, you can practice guests arriving, and him staying calm, several times in repetition. But always have him leashed, until he "unlearns" the craziness, and remembers that he needs to behave.

Does this make sense?