Over a year ago the possibilities of addons werent as limited as they are today... In those days there was a command for getting the distance to enemies, nowadays it only works for friendly targets...

Also you cannot use playernames as a UnitID (which is required in those commands), who are not in your party or raid.

The "best" possibility is the mouseover as UnitID, as in the arena addons, where the enemies are after a mouseover listed in a frame... but I think you wont always cover the hole screen of all wow windows with your mouse