I am trying out four resto shaman, for stacking riptides, mana efficiency and four healing stream totems!

I'm set for passive healing and dps, but I want to dps whilst they round robin a heal.

like

Heal, LB, LB, LB
LB, Heal, LB, LB
LB, LB, Heal, LB
LB, LB, LB, Heal

It'd be easy if I could use cast sequence, how would I setup the target? or is there another way - cheers