Bar change on target

[Mock]

Hey, I've been looking around after an addon or something around that which changed my main actionbar on target, lets say I'm a priest with both healing and damage spells.

When I'm not targeting anything or when i target a unit i can harm it should show the normal bar with damage spells. (Bar 1)

When I'm targeting a target i can heal or holding down the selfcast key (would be "alt" for me) it should show the healing spell bar. (Bar 2)

I know it is possible with some addons like dominos, but i want to use the standard ui actionbar or rather nmainbar. Anyone know if that's possible or am I forced to make a bunch of macros?

Mock