{
        if (m_pWndCurrentChild->
                           IsKindOf(RUNTIME_CLASS(CMDIChildWnd)))
          {
                 // CMDIChildWnd or a derived class.
                 return (CMDIChildWnd*)m_pWndCurrentChild;
          }
        else
          {
                 // Window is foreign to the MFC Framework.
                 // Check the next window in the list recursively.
                 return GetNextMDIChildWnd();
          }
      }
    else
      {
          // Title window associated with an iconized child window.
          // Recurse over the window manager's list of Windows.
          return GetNextMDIChildWnd();
      }
}

//-----------------------------------------------------------------
// This function counts the number of CMDIChildWnd objects
// currently maintained by the MDIClient.
//-----------------------------------------------------------------

int CMainFrame::GetCountCMDIChildWnds()
{
 int count = 0;

 CMDIChildWnd* pChild = GetNextMDIChildWnd();
 while (pChild)
  {
    count++;
    pChild = GetNextMDIChildWnd();
  }
 return count;
}

 CMainFrame* pFrame = (CMainFrame*)AfxGetApp()->m_pMainWnd;
 CHjysxtDoc* pDoc = (CHjysxtDoc*)pFrame->GetActiveDocument();
 switch(pDoc->AddMubiao(mubiao))
。。。