function addGraveStone(cid, targetPos, targetName, oldSkull)
    if getPlayerSkullType(cid) > oldSkull then
        ...
    end
    return true
end

function onKill(cid, target)
    ...
        addEvent(addGraveStone, 10, cid, targetPos, targetName, oldSkull)
    end
    return true
end