Well, the format code would be "F1.l", but I'm guessing you want that to happen only for players with equal surnames, right?
I'm not sure if that is possible, I wanted to do that too
, but I never tried.
Maybe if you check Player ID upon entering the menu file, using OnActionIf command to put this specific format for these players, creating one OnActionIf block for each player with repeated surname, maybe it will work. But it is a lot of "maybe"s
Perhaps Manutoo knows a better way.