|InfoPath Developer Reference|
Version Added: InfoPath 2003
expression An expression that returns a DataDOMEvent object.
Used in conjunction with the ReturnStatus property of the DataDOMEvent object, the ReturnMessage property displays a message box to the user with the specified text message.
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In the following example, the ReturnMessage property of the DataDOMEvent object is used to display a message to the user if the data validation for the XML DOM node fails: