Add not yet defined function/slot from use of it.

It would be really cool to add function to a class through refactor menu the following way.

Suppose I am writing a function which is getting longer. I decide to introduce a new small function which does part of the job. Say I want to call this function say CalculateFactorial( num ).

Notice that I haven't added this function to the class yet but something I want to do but I already wrote it in my function where I want to call it. If I can right click on this proposed function and in refactor menu, I get the option to add this function as member function would be cool. Since it is suppose to be sub-function of sort, by default it should be protected (not public).