This command defines an event called ADRESSCHANGED in a form:
define_evt name(ADDRESSCHANGED) help('This event tells that the #ADDRESS1 field on this form has changed.')
The form also contains a SIGNAL command which triggers this event when the contents of the #ADDRESS1 field on the form are changed:
In this way the form where these commands have been specified can communicate to an owner form that the contents of the #ADDRESS field on it have changed. An owner form can react to this event by having an event routine for it:
See also 7.33.2 DEFINE_MAP with DEFINE_EVT.