If one forgot Retzei in the Bracha Acharona , does one repeat?

One Who forgot to say Retze in the first two meals of shabbat should repeat Birkat Hamazon again, unless he realized his mistake right after he recited the Bracha of "Boneh Yerushalayim" and before he started the next bracha of "Hatov Umetiv", which then he can make up for it with the following special Bracha: "ברוך אתה ה' אלקינו מלך העולם שנתן שבתות למנוחה לעמו ישראל באהבה לאות ולברית ברוך אתה ה' מקדש השבת". If one forgot Retze in the third Shabbat meal, He does not have to repeat Birkat Hamazon. (Shulchan Aruch, Orach Chaim 188,5). Rabbi Binyamin Bamberger