The following code illustrates how to move the file position.

   HMMIO hmmio1;
   MMCKINFO mmckinfo;
   USHORT usFlags;
   USHORT rc;
    ...

   memset( &mmckinfo, '\0', sizeof(MMCKINFO) );
   rc = mmioAscend(hmmio1, &mmckinfo, usFlags);
   if (rc)
     /* error */
   else
    ...