Data check while entering a value in a Quality Collection Plan

Is it possible to have a saved value in a given element in a collection plan checked to see if it had previously been entered? Use case is to check a serial number (non-Oracle controlled) being entered into an element before tabbing through the field to see if it had already been used. Trying to eliminate the duplication of entry. A message to the operator with a hard stop would be ideal.

Thanks in advance