LUA的callcheckscriptex函数怎么一直报错呀

jeepjeep01

attempt to call global 'callcheckscriptex' (a nil value)  stack traceback:
    if callcheckscriptex(actor,"CHECKLEVELEX",">",50) then

    end
这个报错是什么情况呀...那里写错了么? 参数 ">" "50" 这样也不行  '>' '50' 这样传也报错