Okay I give up. Milo my 2yr old JRT can yap for England when anyone comes to the house. It is a really piercing loud yap to so you can't hear yourselves think let alone speak.
I have tried everything I can think of but he is getting worse.
We have tried the removing from the room and bringing in when quiet. Only problem is he doesn't go quiet he stands outside yapping furiously.
Distracting with treats and praising and rewarding when quiet. Problem with that is he is quiet to get the treat but before he has even finished it he is off again.
We have tried ignoring, no eye contact or anything but he gets worse.
Leaving him shut in another room so he can't even get to see the visitor and he yaps the place down.
He is not aggresive in the least all he wants is to be the center of attention, but he won't settle and will leap all over everyone yapping. If they sit down and ignore him, blocking thier lap he will leap onto the back of thier chair and climb on thier head from behind.
He will keep going for hours too. My son was here for over two hours yesterday evening visiting and Milo yapped the whole 2 hours without a break.
Out on walks he never yaps and is friendly to all who want to stroke him and when left in the house when I go out he is quiet.
He does have his moments when I am here alone with him when he will yap for about 10 mins and there is no stopping him.
I have also tried to teach him to bark on command, which was partially succesful except he got so excited I wanted him to bark he wouldn't stop 
Help anyone got anymore ideas please. I'm considering a behaviourist now as its making it impossible to have anyone round now.
My other dog (rottie x GSD) is fine and takes no notice of him and I've never had this with any previous dogs i have owned, including my last JRT

hi at the obedience club i went to she used to tell us in bad cases like yours she used to use a squirty bottle of water and everytime it yapped to use that,i know some people dont agree with things like that but im just saying what she used to tell us to do and i have never been in that kind of position.

As long as the dog is in no way nervous then the squirty botle can act as a mild aversive (unless they like it) and gives you the break in behaviour so you can praise for beign quiet.

Works pretty well with most of my breed.

Does he do this when you are walking him on lead outside the house?  I suspect not.  so I woudl put a lead on him whenever a visitor comes and keep him where you want him so he can't leap at the.  Get him to lie down by you when you are seated.