This is not possible in a macro when you are in combat. So to use it in a DPS sequence is impossible. There are restrictions on what you can use in combat due to unattended gameplay. I don't remember what patch undid this for macros. But I used to have a flash heal rank 3 macro that would automatically heal the lowest in health in molten core.

edit: http://www.wowwiki.com/Category:Worl...cted_Functions