C / C++ / MFC

<br />
BOOL ScreenToClient(<br />
  HWND hWnd,        // handle to window<br />
  LPPOINT lpPoint   // screen coordinates<br />
);<br />
hWnd <br />
[in] Handle to the window <big><font color="red">whose client area will be used </font></big> for the conversion. 

BOOL CMyDialog::OnInitDialog()
{    
  CDialog::OnInitDialog();    
  m_ctlBox.Create(STYLE, CRect(0, 0, 0, 0),this); 
  m_ctlBox.ShowWindow(SW_HIDE); //<-- you could create the window without the WS_VISIBLE style to avoid potential flash doing this    
  //below code to set the position for the CListBox    
  CRect rcOK;    
  GetDlgItem(IDOK)->GetWindowRect(&rcOK);    
  int nBoxWidth = 30;    
  int nBoxHeight = 40;    
  int nxMargin = 10;    
  CPoint BoxUpperLeft;    
  BoxUpperLeft.y = rcOK.top;    
  BoxUpperLeft.x = rcOK.left - nxMargin - nBoxWidth;       

  ::ScreenToClient(this->m_hWnd, &BoxUpperLeft);
  <font color="red">//This code first compulate the CListBox screen coordinate then convert to the Dialog client coordinate</font>   
  
  
  m_ctlBox.SetWindowPos(&CWnd::wndTop, BoxUpperLeft.x, BoxUpperLeft.y, nBoxWidth, nBoxHeight, SWP_SHOWWINDOW);   
  m_ctlBox.ShowWindow(SW_SHOW);    
  return TRUE;
}