As stated by vantalim you need to have it on the healertoon, and need to be controlling that one so will be kinda hard.

If you have the luxery to actually mouse on the healer toon, then just make a mouseover healing macro.

A small example:




#showtooltip Lifebloom
/cast [target=mouseover, help][help][target=player] Lifebloom



I never have anyone selected and it also works on Grids ( like healbot, no clicking, just mouseover )

This also helps to improve your raidhealing ( saves seconds !! ) But harder for Multiboxing, Just buy a G15 keyboard and make life easy.</IFRAME>