Alignment / Position of dialogs based on screen resolution

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VisualC++

I have a dialog based application and have several buttons n which dialog gets created. They are few dialogs that are appearing in the center of my parent dialog but some of the them appearing at different location. Also when I am changing screen resolution most of the dialogs are not appearing on the center. I have used CenterWindow(GetDesktopWindow) but using this also dialogs are appearing on the center of parent dialog. Please suggest whether I need to set parent dialog handle to child window. I am using VS2010 MFC.