QUOTE(Koltz @ Feb 9 2007, 08:17 PM)
If the unit has a speed upgrade use the hero of that unit
EG Devouring one and zerglings
That's the closest you can get without really altering gameplay.
Otherwise you'd have to do something really obscure like use a Queen to designate "Feet" and have your actual unit move to "Feet" every time they're a few grids apart.