The DIALOG control class

Inside the dialog instruction, the predefined keyword DIALOG represents the current dialog object. It can be used to execute methods provided in the dialog built-in class.

For example, you can enable or disable an action with the setActionActive() dialog method, or you can hide or show the default action view with the setActionHidden() method:
BEFORE INPUT
  CALL DIALOG.setActionActive("zoom",FALSE)
AFTER FIELD field1
  CALL DIALOG.setActionHidden("zoom",1)
The setFieldActive() method can be used to enable or disable a field during the dialog:
ON CHANGE custname 
   CALL DIALOG.setFieldActive( "custaddr",
               (rec.custname IS NOT NULL) )