Noob question: How to trigger a script on my target's death?

[macros]

I want my addon to trigger when my target dies. Which event should I use for that? I tried

function ComboWaste_OnEvent() 
    if (event == "UNIT_HEALTH") and (arg1 == "target") then 
        if(UnitIsDead("target")) then
            blahblah();
        end
    end 
end

and

<OnEvent> 
    if (event == "VARIABLES_LOADED") then  
        ComboWaste_initialize(); 
    end 
    ComboWaste_OnEvent(); 
</OnEvent>

But this doesn't really seem to work. I'm new at this, so forgive me if I made some stupid mistake or if the whole thing doesn't make any sense at all. =)

[macros]

Never mind, i got it to work...