Problem with repaint tab in TabControl

Hello, I have probably basic problem but I don't know how to resolve it. I use CXTPTabControl and in OnInitDialog() function insert 2 tabs into it and settings tab parameters. Each tab contains different dialog in different class as it's content. Problem is that when I switch in result program between particular tabs, it doesn't work correctly their repainting. In new tab stay content of previous tab, but when I drag over this window some other application, it's their content repaint and content is correctly already. I try to look to similar examples as TabManager or Toolbox but I can't find out which control is necessary to use to invoke repainting content of dialog when the select tab is changed (if it's necessary to do in class which contains cxtptabcontrol and classes of dialogs or in each dialog class). Can you help me, please ? Thanks

Example of inicialization of CXTPTabControl content:
BOOL CTest::OnInitDialog()  
{
        CXTPTabPaintManager* mgr = m_TabCtrl.GetPaintManager();
       //style settings
        mgr->SetAppearance(xtpTabAppearancePropertyPage2003);
        mgr->m_bBoldSelected = true;
        mgr->m_bOneNoteColors = true;

        m_TabCtrl.ModifyStyle(0,     WS_VISIBLE|WS_ CHILD|SS_NOTIFY|WS_CLIPCHILDREN|WS_CLIPSIBLINGS);
        //image list settings
        CImageList m_ilTabCtrl;
        m_ilTabCtrl.Create(16,16, ILC_COLOR32|ILC_MASK, 0, 2);
        m_ilTabCtrl.Add(AfxGetApp()->LoadIcon(IDI_AVSTATISTICS));
        m_ilTabCtrl.Add(AfxGetApp()->LoadIcon(IDI_AVASOPTIONS));
        m_TabCtrl.SetImageList(&m_ilTabCtrl);
      
        //inserting particular class to tab control
        CString res_str = _T("");       
        int nTab = m_TabCtrl.GetItemCount();
        res_str.LoadString(IDS_NAME_STATISTICS);

        m_pASStatistics.Create(CStatistics::IDD, &m_TabCtrl);
        m_TabCtrl.InsertItem(nTab, res_str, m_pASStatistics, 0);
        nTab++;

        res_str = _T("");       
        res_str.LoadString(IDS_NAME_OPTIONS);

        m_pASSOptions.Create(COptions::IDD, &m_TabCtrl);
        m_TabCtrl.InsertItem(nTab, res_str, m_pASSOptions, 1);

        m_TabCtrl.ShowIcons(TRUE);

        return TRUE;
}

Thanks for your reply, but it doesn't work. I look that TCN_SELCHANGE is used in CXTTabCtrlBaseEx and it isn't possible to use in CXTPTabControl. Even if I try to used it as it's in example in manual, it doesn't work, this function wasn't use (I verify it by breakpoint and by tab item changing).
I use:
//{{AFX_MSG_MAP(CTest)
ON_MESSAGE(TCN_XT_SELCHANGE, OnTabSelChange)
//}}AFX_MSG_MAP

LRESULT CTest::OnTabSelChange(WPARAM wParam, LPARAM lParam)
{
    CXTPTabControl* pTabCtrl = (CXTPTabControl*)lParam;
    ASSERT_VALID(pTabCtrl);

    int nID = (int)wParam;
    if (nID == IDC_ONACCESSTAB)
    {        
         &nbs p;  Invalidate(FALSE);
    }
    return 0;
}
In other hand I find out that class CXTPTabManager from which is derived CXTPTabControl contains method virtual void OnItemClick( CXTPTabManagerItem* pItem ). I hope that it's the right method but I'm not sure how to used them by correctly way. It isn't neither message in manual to assign this method to message map and neither example in samples. I tried to use it this way, but it didn't work, method wasn't call by tab item changing:
void CTest::OnItemClick(CXTPTabManagerItem* pItem)
{
    Invalidate(FALSE);
}
Please can you help me?

Thanks for your response but I find out problem and resolved it myself (in cooperation with my colleague). Problem was that I have in both dialogs GroupBox. If we set a Transparent property to these groupboxes, problem was resolved and dialogs are repainted correctly.