At a sheva Brachos during the week, is it permissible to call a person off the street to be a panim chadashot or must he partake in the seudah?

It is permissible to call a person off the street to act as a Panim Chadashot. Though, the Panim Chadashot must eat the last course with the rest of the group and join the Mezuman in order that he may answer the Sheva Brachot and be Panim Chadashot. Rabbi Yosef Weitzen