When you develop more complex GUI applications, you will begin to code subforms and you will run up against the problem of how to get the information that the user typed into the subform back into the main form. It is generally advisable to keep the communication with the back-end application logic restricted to the main form, and hence you end up with something like the diagram below.

I have put together a short document that shows how to get information from a subform to the mainform. The most important thing is that the subform exposes a method that the main form can call. This method returns the data that has been entered into the subform. Please read the document.

How to pass information from a subform to the main form