You get your friend to tell him all of this.. the one you said who was willing to talk to him... YOu tell him NOTHING
Your friend tells him something like
"She is willing to work things out with you, even after the way you have been treating her... But there is NO way she's going to move an INCH of ground while you are in contact with this "friend" of yours. I don't CARE if its an emotional affair or a physical one.. this woman has go to go, or you will lose your family and your friends and everything that is important to you..."
Your husband will likley throw her his denial script...
Your friend just has to say
"This woman is NOT welcome by your wife... regardless of what she and you are or are NOT doing... I really don't CARE if you're cheating.. your WIFE is HURTING and you are putting this woman AHEAD of your wife... THAT needs to STOP or she is NOT going to talk to you ... AT ALL"
"This woman is married and she likley has problems of her own, you are in no shape to help her... you both need to cut the chord and work on your marriages"
"If you want to talk, you can always come to me, day or night.. But your wife does NOT want to SEE you until this woman is GONE.. got it?"
if you can find a friend to give him a talk like that you are gold
