How to change CMFCToolBar runtime

I need under certain conditions to switch toolbars in my SDI application using the same CMFCToolBar object, which is the member of CMainFrame. I'm trying to do it like this:

void CMainFrame::ChangeTlbr(const int tlbIdx)
{
    m_wndToolBar.ResetImages();
    switch (tlbIdx)
    {
        case 0 :

            m_wndToolBar.LoadToolBar(IDR_TLBR1);

            break;
        case 1:

            m_wndToolBar.LoadToolBar(IDR_TLBR2);

            break;
    }

    m_wndToolBar.Invalidate();
    m_wndToolBar.UpdateWindow();
}

But bitmap of the next toolbar is not loaded.

What am i doing wrong in this case, and if there is better way to do this?

The following function shows how to replace the current toolbar by another one, defined as IDR_MAINFRAME1:

void CMainFrame::OnChangeToolbar()
{    
    m_wndToolBar.ResetAllImages();
    m_wndToolBar.LoadToolBar(IDR_MAINFRAME1);
    m_wndToolBar.LoadBitmap(IDR_MAINFRAME1);
    m_wndToolBar.AdjustSizeImmediate();        
}