Parent and child GUI actions

GUIDE is good for creating a straightforward GUI, but for something with more complexity I think creating them in code is easier.

In this code I show how to create a "parent" GUI and place a "child" GUI onto it. In the example, both parent and child have their own pushbutton controls, but it shows how the parent can call a function that belongs to the child.

Note that this is part of a larger project to make more space available on a GUI. By creating more than one child GUI on the same part of the parent, and setting/unsetting their 'Visible' property, you can emulate the kind of tabbed pages you get in Windows apps.

This is my first attempt to post an example so please excuse any etiquette offenses, etc.