Z-ordering of an SDI application with modeless CDialog - Microsoft Visual C & C++

Hello, I have some modeless CDialogs in my application. My main window is a SDI application (CFormView in a CFrame) My problem is that my CDialog that are not modeless are always on top of my main window, I tried to create them with NULL as parent or CWnd::GetDesktopWindow() but it does not seem......(with 4 answers.)