AfxMessageBox windows message

Thanks.  Would the AfxMessageBox function couse the OnActivatefunction to be called?  My problem is that I want my dialog fullscreen.  I have a tab control in my dialog and it is doing something funny as the dialog does not go fullscreen once the tabs dialogs are created.  If I put in AfxMessageBox in my OnInit then after I press OK it goes fullscreen.

BOOL CMyClass::OnInitDialog()
{
      SHINITDLGINFO shidi;
      shidi.dwMask = SHIDIM_FLAGS;
      shidi.dwFlags =SHIDIF_FULLSCREENNOMENUBAR;
      shidi.hDlg = m_hWnd;
      ::SHInitDialog(&shidi);

      SetForegroundWindow();

      SHFullScreen( m_hWnd, SHFS_HIDESTARTICON|
      SHFS_HIDETASKBAR|
      SHFS_HIDESIPBUTTON );

      MoveWindow(0,0,240,320,TRUE);

      HWND hWnd;
      hWnd = ::SHFindMenuBar(this->m_hWnd);
      ::ShowWindow(hWnd, SW_HIDE);
}

AND
void COptions::OnActivate(UINT nState, CWnd* pWndOther, BOOL bMinimized)
{
     CDialog::OnActivate(nState, pWndOther, bMinimized);

     SHFullScreen( m_hWnd, SHFS_HIDESTARTICON|SHFS_HIDETASKBAR|
                                                SHFS_HIDESIPBUTTON );

     MoveWindow(0,0,240,320,TRUE);

     HWND hWnd;
     hWnd = ::SHFindMenuBar(this->m_hWnd);
     ::ShowWindow(hWnd, SW_HIDE);

}

I create the dialogs for my tab control in the OnInit of my dialog like so:
//Tab Options
     dlgTab1Dlg = new CTab1(this);
     dlgTab1Dlg->Create(IDD_TAB1_DIALOG, this);
     dlgTab1Dlg->SetParent(&m_tabOptions);
     dlgTab1Dlg->ShowWindow(SW_SHOW);
     dlgTab1Dlg->SetWindowPos(NULL, rTab.left, rTab.top, rTab.Width(), rTab.Height(), SWP_NOZORDER);

     dlgTab2Dlg = new CTab2(this);
     dlgTab2Dlg->Create(IDD_TAB2_DIALOG, this);
     dlgTab2Dlg->SetParent(&m_tabOptions);
     dlgTab2Dlg->ShowWindow(SW_SHOW);
     dlgTab2Dlg->SetWindowPos(NULL, rTab.left, rTab.top, rTab.Width(), rTab.Height(), SWP_NOZORDER);

The above OnInit should be:
BOOL CMyClass::OnInitDialog()
{
//Tab Options
     m_tabOptions.InsertItem(0, _T("Tab 1"));
     m_tabOptions.InsertItem(1, _T("Tab 2"));
......
.....
     dlgTab1Dlg = new CTab1(this);
     dlgTab1Dlg->Create(IDD_TAB1_DIALOG, this);
     dlgTab1Dlg->SetParent(&m_tabOptions);
     dlgTab1Dlg->ShowWindow(SW_SHOW);
     dlgTab1Dlg->SetWindowPos(NULL, rTab.left, rTab.top, rTab.Width(), rTab.Height(), SWP_NOZORDER);

     dlgTab2Dlg = new CTab2(this);
     dlgTab2Dlg->Create(IDD_TAB2_DIALOG, this);
     dlgTab2Dlg->SetParent(&m_tabOptions);
     dlgTab2Dlg->ShowWindow(SW_SHOW);
     dlgTab2Dlg->SetWindowPos(NULL, rTab.left, rTab.top, rTab.Width(), rTab.Height(), SWP_NOZORDER);


      SHINITDLGINFO shidi;
      shidi.dwMask = SHIDIM_FLAGS;
      shidi.dwFlags =SHIDIF_FULLSCREENNOMENUBAR;
      shidi.hDlg = m_hWnd;
      ::SHInitDialog(&shidi);

      SetForegroundWindow();

      SHFullScreen( m_hWnd, SHFS_HIDESTARTICON|
      SHFS_HIDETASKBAR|
      SHFS_HIDESIPBUTTON );

      MoveWindow(0,0,240,320,TRUE);

      HWND hWnd;
      hWnd = ::SHFindMenuBar(this->m_hWnd);
      ::ShowWindow(hWnd, SW_HIDE);
}