What Rakradu said. Stand in the middle, target an injured person, start your bandaging, scan and select your next target while it's channeling, and click your hotkey again as soon as you've finished channeling one. The channeling bar should be running constantly - while you're healing one, you should be scanning for the next.
You really don't need a macro, just keep the bandages on a hotkey.
If you do this in a group with two people, one healing each side, it's super easy, and if you have a group of three it's downright trivial.
Edited, Jan 8th 2007 10:43am by fledarmus