A basic macro will be to Focus the lead toon, with every toon (lead included).

For a five boxer, have five focus macros.
Everyone (on Keybind A) focuses Toon A; Keybind A also switches to the region Toon A is in... ie, Warcraft Keybind for the Focus macro and boxing software Keybind for the region switch.

Then attack with:
/cast [@FocusTarget] Whatever

Heal with:
/cast [@FocusTarget,Help][@FocusTargetTarget,Help] Whatever

Follow with:
/Follow [@Focus]

@ is the same as Target=
Depending on your software, you might have auto follow options etc.
Also take a look at the Jamba (addon), if you haven't already.