Go4Expert - Detecting a window within another window

I am trying to write an app using MFC which allows me to drag small dialogs around and drop them in static windows within a main dialog. The idea is, the small dialogs represent workers and the static windows represent work positions. The problem I am having is when I drop the second dialog in the same static window, it simply overlaps the first dialog so you can't tell there are two dialogs ( or three or four etc.).
I have been using this code to try and detect when the static has a dialog in it:

Code:

void CBoxes1Dlg::OnLButtonUp(UINT nFlags, CPoint point) 

{

        CRect rect;

        CWnd *pWnd1;

        CPoint pt;

        int y=0;



        CWnd *pWnd = ChildWindowFromPoint(point);

        if(pWnd!=NULL) {

                pWnd->GetWindowRect(rect);

                ScreenToClient (rect);

                pt.x=rect.left+5;

                pt.y=rect.top+5;

                pWnd1=pWnd->ChildWindowFromPoint(pt,CWP_ALL);

                

                if(pWnd1 == pWnd){

                        // no dialog in this static box

                }else{

                        // handles don't match so must be a dialog in the static already

                }

        }

        m_person->SetWindowPos(&CWnd::wndTop,(pt.x),(pt.y),0,0,SWP_NOSIZE|SWP_NOZORDER);

}

This doesn't work properly.....
Anyone see the problem or think of an easier way to do it.

Thanks
Zapper