Lock file set (INT 21h, CBh - Novell NetWare 4.0)

        Entry:
          AH = CBh
            if function C6h lock mode 00h:
                DL = mode
                      00h  No wait
                      01h  Wait
            if function C6h lock mode 01h:
                BP = timeout in timer ticks (1/18 sec)
        Return:
          AL = error code