This example transfers a pointer from the application-defined data area of a dialog window to the application-defined data area (window word) of a main window. The pointer is then retrieved.

#define INCL_WINWINDOWMGR
#include <OS2.H>

HWND hwndClient;
ULONG  msg;
MPARAM pParm, mp1, mp2;

/* Inside dialog procedure */
switch( msg )
{
  case WM_INITDLG:
       /* This points to the data area and is passed by */
       /* WinLoadDlg, WinCreateDlg, and WinDlgBox       */
       /* in their pCreateParams parameter.             */
       pParm = (MPARAM)mp2;

       /* Place the pointer in the window word area */
       WinSetWindowULong(hwndClient,
                         QWL_USER,
                         (ULONG) pParm);

       case WM_COMMAND:
            switch (SHORT1FROMMP(mp1))
            {
              case DID_OK:
                   /* Retrieve the pointer from the window word area */
                   pParm = (MPARAM)WinQueryWindowULong(hwndClient,
                                                       QWL_USER);
            }
}