Abstract: The invention is for auditing the value of a change for at least one non used portion of an interline ticket in a networked travel reservation system including programmed processor performing receiving a request for a change for at least a non-used portion of an interline ticket; calculating the prorated amounts for the original itinerary (Refund) and both the original and new itineraries (Exchange); authorizing the change upon the validating airline ticket's balance being equal or greater than a predefined threshold; and triggering an event upon the validating airline ticket's balance being less than a predefined threshold.