This message is sent by a MIDI input driver to a client application to return a system-exclusive input buffer to the application.
DWORD dwParam1
Specifies a far pointer to a MIDIHDR structure identifying the input buffer.
DWORD dwParam2
Specifies the time that the data was received by the input device driver. The time stamp is specified in milliseconds, beginning at zero when the driver received the MIM_START message.
There is no return value.