This message notifies an application that the use of a device is being gained or lost.

MsgParam1
     USHORT  usDeviceID  /*  Device ID. */
     USHORT  usReserved  /*  Reserved. */

MsgParam2
     USHORT  usEvent     /*  Gaining or losing use of device. */
     USHORT  usReserved  /*  Reserved. */