The name of the Webroutine to be invoked after a selection has been made in the prompter.
Blank – no Webroutine is invoked when a selection is made in the prompter.
The name of a Webroutine in single quotes. The Webroutine must exist in the WAM specified in the on_change_wamname property. A list of known Webroutines can be displayed by clicking the corresponding dropdown button on the property sheet.