AT_ERRCOUNT ACCUAPI IG_GUI_select_track_mouse ( 
        HIGEAR hIGear, 
        DWORD dwGrpID, 
        HWND hWndImage, 
        INT nX, 
        INT nY, 
        LPFNIG_GUISELECT lpfnSelect, 
        LPVOID lpPrivate 
);

PFNIG_GUISELECT   MyGUISelectCB;/* Called when rect delineated  */
HIGEAR  hIGear;/* HIGEAR handle of image     */
struct  tagMyPriv  {
   BOOL     bRectWasSelected; /* TRUE=User delineated a rect  */
   AT_RECT  rcUserRect:      /* This is the rectangle      */
   }         PrivateStruct;  /* Name of private data area    */
/* Window-message handling routine:    */
LPARAM CALLBACK  MsgHandler
        ( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
 ...
switch ( msg )
  {
  CASE WM__LBUTTONDOWN:
         ...
        IG_GUI_select_track_mouse ( hIGear, IG_GRP_DEFAULT, hWnd, 
        LOWORD(lParam), HIWORD(lParam), MyGUISelectCB, 
        (LPVOID) &PrivateStruct );
         ...
  }
 ...
}
VOID ACCUAPI  MyGUISelectCB ( LPVOID lpPrivate, 
        LPAT_RECT lprcRectSelected )
/* This function will record the rectangle selected, in PrivateStruct, pointed to by
lpPrivate. */
{
struct tagMyPriv *   structPtr; /* Will point to PrivateStruct */
structPtr =  lpPrivate;      /* Copy the pointer */
structPtr -> bRectWasSelected  =  TRUE; /* Indicate a rect here */
structPtr -> rcUserRect        =  *lprcRectSelected;  /* Copy rect */
return;      /* Done */
}