Dialog Application to Hide

VS2008 C++, MFC

I want a dialog type app to be hidden when executed. I've done some reading
and I think I added all the necessary items to do this, but it still
displays itself when executed. This is what I've done so far. I understand
that a dialog, by design, will be set to "WM_SHOW" at the end of the
OnInitDialog(), therefore I must call WM_WINDOWPOSCHANGED (based on what
I've read). I can walk through the code and it steps into the
WM_WINDOWPOSCHANGED but I can't tell if the flag changes. Can anybody help
me. I'm guessing a changes were made to VS2008 that prevents dialogs from
starting up as Hidden.

//.h file
Created a variable:
protected:
            BOOL m_bVisible;

public:
    BOOL IsVisible(void) { return m_bVisible==true; }
    void SetVisible(BOOL b) { m_bVisible = b; }
    BOOL GetVisible(void) { return m_bVisible; }

//.cpp file

Constructor:
m_bVisible(FALSE);

//Message Map
BEGIN_MESSAGE_MAP(CMyTrayDlg, CDialog)
    ON_REGISTERED_MESSAGE( UWM_TRAY_CALLBACK, OnTrayCallback )
    //}}AFX_MSG_MAP
    ON_WM_WINDOWPOSCHANGED()
    ON_COMMAND(ID_FILE_HIDE, &CMyTrayDlg::OnFileHide)
    ON_COMMAND(ID_FILE_RESTORE, &CMyTrayDlg::OnFileRestore)
    ON_COMMAND(ID_FILE_EXIT, &CMyTrayDlg::OnFileExit)
END_MESSAGE_MAP()

//handles message WM_WINDOWPOSCHANGED
void CMyTrayDlg::OnWindowPosChanged(WINDOWPOS* lpwndpos)
{
    if( !IsVisible() )
        lpwndpos->flags &= ~SWP_SHOWWINDOW;

    CDialog::OnWindowPosChanged(lpwndpos);

    // TODO: Add your message handler code here
}