1.CDO>  DEFINE FIELD AMOUNT_OWED
      cont>   DATATYPE IS UNSIGNED WORD
      cont>   VALID IF AMOUNT_OWED > 0.

      In this example, the VALID IF field property in the DEFINE
      FIELD command specifies a range of valid values for the AMOUNT_
      OWED field element.

    2.CDO>  CHANGE FIELD AMOUNT_OWED
      cont>   NOVALID IF.

      In this example, the NOVALID IF keywords remove the VALID IF
      property from the AMOUNT_OWED field element.