You want to use one of:
a) Healbot; or
b) Vuhdo; or
c) Grid + GridCustomLayouts + Clique
A & B are stand alone options, C requires all three of those addons; either option is as good as the others, it comes down to visual preference.
My Custom Layout is here: http://www.dual-boxing.com/threads/4...870#post347870

You need an alphabetical sort, so the frame is identical in order and positioning on every window.
That way the second name down, on any screen you click in, is also the second name down (same target) on your healer's screen.

Once you have that, you need a 'Repeater Region' over the entire Grid Frame.
That is what it is called, with IS Boxer.
You can make a 'Repeater Region' with Hot Key Net, even if you don't use HKN for anything else, and it will work in conjunction with whatever software you box with; see: http://www.dual-boxing.com/threads/3...rthquake/page2