Scripts

Could you please tell me what is wrong here:

function BiaraKill()
while 1 do
sleep(10);
if IsHeroAlive("Biara") == nil then
SetObjectiveState("obj2", OBJECTIVE_COMPLETED);
Sleep(2);
break;
end;
end;
end;

startThead("BiaraKill);

I need the task obj2 to be completed after Biara dies. Thank you in advance...