About functions for windows and controls – PB Docs 2019

PowerBuilder provides built-in functions that act on windows and
on different types of controls. You can use these functions in scripts
to manipulate your windows and controls. For example, to open a
window, you can use the built-in window-level function Open, or you
can pass parameters between windows by opening them with the function
OpenWithParm and closing them with CloseWithReturn.

You can define your own window-level functions to make it easier
to manipulate your windows. For more information, see Working with User-Defined Functions.