Macro HelpFollow

I am a Lvl 90 Medic and I would like to create a buff macro so I can stand outside a starport or other facility and give buffs to player going by. I can't see to figure out how to untarget one player and give a buff to another...my macro keeps buffing the person I first buffed until they are out of range. Can someone please help me with this?

Thanks Bunches,
Your friendly neighborhood medic!