The Form class
The ui.Form class provides an interface to form objects created by
          an OPEN WINDOW WITH FORM or DISPLAY FORM
          instruction.
A form object allows you to manipulate form elements by program.
For example, you can hide       parts of a form with the setElementHidden() method.
The runtime system is       able to handle hidden fields during a
dialog instruction. You can, for example, hide a         GROUP containing
fields and labels.
Outside dialogs, get a ui.Form 
     instance of the current form with the ui.Window.getForm() method.
When executing a dialog, use the         ui.Dialog.getForm() 
     method.
Note that the OPEN
        FORM instruction does not load a form; it
simply declares a handle. The form       will be created in the AUI
tree when executing the DISPLAY FORM 
     instruction. Therefore, the corresponding ui.Form object
is only available       after DISPLAY FORM is executed.