The nominated webroutine will be invoked whenever the Previous or Next image / button is pressed.
Default value
Not applicable – a Webroutine name must be specified.
Valid values
The name of a Webroutine in single quotes. The Webroutine must exist in the WAM specified in the on_click_wamname property. A list of known Webroutines can be displayed by clicking the corresponding dropdown button on the property sheet.
