DOS Internal - Set extended error info???

        Entry:
          AX = 1222h
          SS:SI -> 4-byte records
                BYTE    error code, FFh = last record
                BYTE    ??? FFh = don't change
                BYTE    ??? FFh = don't change
                BYTE    ??? FFh = don't change
        Return:
          nothing???

        Note:   can be called only from within DOS