They removed the "Thinking" macros from WoW right before BC. This was a effort to stop the Bots.

Use Healbot addon and you wont have a problem at all. It allows you to click on bars to heal sertain members and the bars can be set to "Light up" at what ever level of health you desire. very nice addon as you can set several spells to go off on clicks, alt+click, ctrl+click ect....

Go Healbot and you will fall in luv with it after your first big pull.