The DBT_USERDEFINED device message identifies a user-defined system message.
To send the DBT_USERDEFINED device message, send the WM_DEVICECHANGE message with wParam set to DBT_USERDEFINED and lParam set as described following.
dwData = (DWORD) lParam;
Parameters
dwData
Address of the user-defined data. The data must be in the format specified by the _DEV_BROADCAST_USERDEFINED structure. lParam is application-defined. May be zero.
See Also