well for the situation you described I would try the following:

Code:
<Hotkey LButton>
 <If MouseIsOverWindowRect Pally 200 200 100 100>
        <SendLabel shaman>
              <Key 6>
 <Else If MouseIsOverWindowRect Pally 200 300 100 100>
        <SendLabel shaman>
             <Key 7>
 <Else>
            <ClickMouse>
and you would bind the 'LB my target' to a button activated by 6, and the 'healing wave on pala' to 7 on the shaman.

EDIT: damn, freddie beat me ;)