Such functionality could be achieved in a WebService binding scenario, where you could assign a custom attributes to the items, from the datasource. Thus, at the OnClientEntryAdding client-side event, you could set the custom text - Client Name - City, State
. In addition, in the same event, you could check if there is already another item with the same text and determine weather to set the Client Name - City, State (Terminated Date)
Bellow you could find a sample project, which I had created for you, demonstrating a possible implementation.
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