This function sends a message to the dialog item defined by idItem in the dialog window specified by hwndDlg.

#define INCL_WINDIALOGS /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND       hwndDlg;    /*  Parent-window handle. */
ULONG      idItem;     /*  Identity of the child window. */
ULONG      msg;        /*  Message identity. */
MPARAM     mp1;        /*  Message parameter 1. */
MPARAM     mp2;        /*  Message parameter 2. */
MRESULT    mresReply;  /*  Message-return data. */

mresReply = WinSendDlgItemMsg(hwndDlg, idItem,
              msg, mp1, mp2);