Is there a set up in Nav 2013 that enables us to tell Nav to NOT allow duplicates of External Document No in Sales HEader and Sales Shipment Header? Basically, when user goes into Sales Order Card, as they enter the external Document No, which is usually the Customer PO Number, we want to validate this external document no and make sure it wasn't already used in some records in the Sales Header Table. I gather we can just validate the Sales HEader Table and no need to validate against sales Shipment Header.
If there are no set up available in Nav, I can just go into the Sales HEader Table design and write my validation on the OnValidate event. OR do you recommend OnLookup? Please advise.
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