URGENT !!! Problem with Windows (WM_ACTIVATE)

Hi Gurus
I have got the following problem: In my MDI app I have a SplitterWnd and two views (TreeView and FormView). In this FormView I have a PropertySheet with pages which is resizing. I have only one problem with this: When I have more than one Docs (Views) open and close the top one, the FormView is not activated. (no WM_ACTIVATE Message). My question is: How can I get the view which will be activated when I close the top one ??? and can I simply post a WM_ACTIVATE or WM_SIZE message to it ???
thanx a lot for help
cu

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