The MCI_MARK command records or erases marks that can be used with the MCI_SEEK command for high-speed searches. VCR devices recognize this command.
MCIERROR mciSendCommand(MCIDEVICEID wDeviceID, MCI_MARK, 
    DWORD dwFlags, (DWORD) (LPMCI_GENERIC_PARMS) lpMark);
 Returns zero if successful or an error otherwise.
The following additional flags apply to VCR devices:
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in mmsystem.h.
MCI Overview, MCI Commands, MCI_GENERIC_PARMS