[code:1]/focus fatality
/cast [target=focustarget] Greater Heal[/code:1]

But you only need the focus part once, so if you have that set to say button 1. The heal macro would be

[code:1]
#showtooltip
/cast [target=focustarget] Greater Heal
[/code:1]

#showtooltip - Use the questionmark icon when making the macro, then you get the icon for the greater heal and the correct tooltip (as opposed to the macro name).

[target=focustarget] - The target of this spell will be cast on my focus' (Fatality's) target. (IIRC)