There's no telling ...  没法知道……

　　There's no way to tell who it was. 没办法知道是谁做的。

　　There's no telling what you think. 没办法知道你在想什么。

　　There's no telling how long they'll last. 不知道他们会持续多久。

　　Do you think the new business will succeed? 你觉得新生意能成功吗?

　　There's no telling what happen to it.  没办法知道将来会发生什么事。