You can't stop anyone from doing anything that they want to do.
Your man is the one who betrayed you! Even if this woman moved across country there is nothing keeping your man from finding a replacement. If your man is "serious" about putting the affair in the past. (HE) would do everything within his power to show you and reassure you that he will never hurt you like that again. You shouldn't have to do anything!
The person seeking forgiveness is suppose to show contrition. They are suppose to be the one bending over backwards to get back into YOUR good graces. If this is not the case with your relationship you might be "forgiving" someone who is not really "remorseful". A lot of people "forgive" cheaters as an automatic reflex. They can't bare the thought of being cheated on and ending the relationship at the same time.
A few weeks go by, anger and resentment creep in. Even if their partner is doing everything to prove their loyalty the "trust" doesn't come back for a very long time. Sometimes they become angry at themselves because they "forgave" their mate. They feel as though they gave them a "free pass". Others wonder if things had been the other way around would their mate had forgiven them. If the answer is "no". It makes them even angrier. The person who is less "emotionally invested" in the relationship has the real power.
If you're trying to lose weight you don't tell the grocery store to stop carrying cakes and pies! (YOU have to exercise self-discipline). Your desire to confront the other woman is an admission that (You Don't Trust Your Man) to shut her down. Unless your man asks you for your help in this matter you should stay out of it. Don't give the other woman the satisfaction of believing she has the power to take your man away from you by begging her to stay away. Your man is the one that has to get her out of his life.