AH II has padlock, precisely as you want. There is padlock for enemy planes and padlock for friendlies. I forget the keys now since I use Track IR, but you get exactly the performance you are asking for. The box around the icon indicates the plane that should be padlocked. Sometimes I've had the box appear but without padlock, but then after going through the setup again it eventually works. So read the help and try again.
Best Regards.