long pascal SendDlgItemMessage(HDLG hDlg, WORD idItem, WORD msg, WORD wParam,
                                              DWORD lParam)

  This functions sends a message to a specified control within a
dialog box.

Parameters
  hDlg is the handle of the dialog box which contains the specified control.
  idItem is the identifier of the control that we want to send the
   message to. (The id is not the same thing as the handle.)
  msg, wParam, and lParam are the standard message parameters to
      be sent to the dialog item.

Returns
  FALSE if the message couldn't be sent. Otherwise, the value passed
back from the control's window procedure is returned.