Can I stop my future ex-wife from having her boyfriend in our house while I am home?

The first thing that crosses my mind is a restraining order but you need to have grounds for that.  His presence per se is not harrassment albeit uncomfortable and maybe even bad mannered.  I would speak with your attorney in the divorce matter and have himor her speak with the attorney for your wife and see if an agreement of some sort can be had if there are no grounds for any other legal document that could enforce your wishes.  When you speak with your attorney give him or her all the facts and factors that surround your situation and see what he or she can come up with for you.  Good luck.