Can I take a message for him?

我能为您给他捎个口信吗？

I don't know, but he will certainly be back for lunch. This is his wife speaking. Can I take a message for him?

老外说她也不知道，但是她大概说了个时间，然后可以说下自己是谁，这样方便以后信息的正确流动，然后可以主动问下对方需要转告信事情不。