2.2.7.5 AsyncUICustomUI
AsyncUICustomUI is a string that contains a well-formed XML document ([XML1.0] section 2.1).
The root element of the document MUST be an asyncPrintUIRequest element (section 2.2.7.1.1). A customUI element MUST be nested within the asyncPrintUIRequest markup at the point where it is referenced in the XML schema.
AsyncUICustomUI (or the similar AsyncUICustomData) SHOULD be used by a printer driver on a server when it requires client-side handling of an event or a change in device status that cannot be expressed by using an AsyncUIMessageBox or AsyncUIBalloon notification. The AsyncUICustomUI notification calls for the execution of client-resident code that is associated with the server-resident printer driver.