Disabling close button on CMDIChildWnd

I am writing a MDI application that has multiple document templates.  On start up, there is one document type that I want to open and not let the user close/destroy.  I want to disable the close button (X) in the corner of the CMDIChildWnd.  I have seen how to use PreCreateWindow to change the style for the minimize and maximize controls;  but I haven't figured out how to disable the close.

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Tommy HuiConnect With a Mentor EngineerCommented:
You'll need to catch the WM_SYSCOMMAND and check wParam parameter. If
  if ((wp & SC_CLOSE) == SC_CLOSE)
    // ignore
    // call base class

dembowskisAuthor Commented:
Well, that wasn't exactly the answer I was looking for.  But it was enough of a hint that I got going in the right direction. And since you saved me a lot of time, I graded it high.

Your response would ignore the SC_CLOSE, but my question was how do I -DISABLE- the close button.  Researching the information on WM_SYSCOMMAND and SC_CLOSE got me on the GetSysMenu method and the following solution, which I placed in the OnActivateMdiFrame:

CMenu *lwSysMenu = GetSystemMenu( FALSE );
lwSysMenu->EnableMenuItem( SC_CLOSE, MF_BYCOMMAND | MF_GRAYED );

Thank you!!

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