another way:

 My application has "vcr" buttons in the toolbar, and text next to it "item X of Y"

 the way I do it is to create a dummy toolbar button, like you did and an UPDATE_COMMAND_UI handler.  When I update my variables, the text "updates itself".

 ON_UPDATE_COMMAND_UI(ID_DUMMY2, OnUpdateDummy2)

void CTabFrameWnd::OnUpdateDummy2(CCmdUI* pCmdUI)
{
 CString cs ;
   cs.Format("Seq %d of %-d",    m_seqnum, m_totrecs-1) ;

 // Add text to the toolbar button.
 m_wndToolBar.ModifyStyle(0, TBSTYLE_LIST) ;
 m_wndToolBar.SetButtonText(m_wndToolBar.CommandToIndex (ID_DUMMY2), cs);
 
}