The name of the Webroutine to be invoked when an item in the list box is selected.
Blank – a Webroutine is not invoked when an item is selected.
A Webroutine name, in single quotes. This Webroutine should exist in the WAM specified in the on_select_wamname property. Click on the corresponding dropdown button in the property sheet to choose from a list of known Webroutines.