VC 多文档MDI程序如何让它每次只能打开一个文档的实例？？？？

[laozhuang]

请各位VC高手帮帮忙！！！
VC 多文档MDI程序如何让它每次只能打开一个文档的实例？？？？

我在做一个VC MDI多文档的程序时，想让每个文档模板
每次只能运行一个实例或者说每个文档每次只能打开一
个实例。不能打开第二个实例，我应该在什么地方添加
什么限制的代码？
请注意，不能用SDI程序来代替！！！

在CMytestApp类的InitInstance()中有如下代码：

BOOL CMytestApp::InitInstance()
{

if (!AfxSocketInit())
{
AfxMessageBox(IDP_SOCKETS_INIT_FAILED);
return FALSE;
}

AfxEnableControlContainer();

// Standard initialization
// If you are not using these features and wish to reduce the size
// of your final executable, you should remove from the following
// the specific initialization routines you do not need.

#ifdef _AFXDLL
Enable3dControls(); // Call this when using MFC in a shared DLL
#else
Enable3dControlsStatic(); // Call this when linking to MFC statically
#endif

// Change the registry key under which our settings are stored.
// TODO: You should modify this string to be something appropriate
// such as the name of your company or organization.
SetRegistryKey(_T("Local AppWizard-Generated Applications"));

LoadStdProfileSettings(); // Load standard INI file options (including MRU)

// Register the application's document templates. Document templates
// serve as the connection between documents, frame windows and views.

CMultiDocTemplate* pDocTemplate;
pDocTemplate = new CMultiDocTemplate(
IDR_HRNBSTYPE,
RUNTIME_CLASS(CHrnbsDoc),
RUNTIME_CLASS(CChildFrame), // custom MDI child frame
RUNTIME_CLASS(CHrnbsView));
AddDocTemplate(pDocTemplate);


………………………………………………………………
CMultiDocTemplate* pCxmxDocTemplate; //查询明细

//查询明细
{
pCxmxDocTemplate = new CMultiDocTemplate(
IDR_HRNBSTYPE,
RUNTIME_CLASS(CMytestDoc), // document class
RUNTIME_CLASS(CMDIChildWnd), // frame class
RUNTIME_CLASS(CCxmx)); // view class
AddDocTemplate(pCxmxDocTemplate);
}
……………………………………………………………………
// create main MDI Frame window
CMainFrame* pMainFrame = new CMainFrame;
if (!pMainFrame->LoadFrame(IDR_MAINFRAME))
return FALSE;
m_pMainWnd = pMainFrame;
/*
//注释掉以便不让程序启动时出现新建的空文档
// Parse command line for standard shell commands, DDE, file open
CCommandLineInfo cmdInfo;
ParseCommandLine(cmdInfo);

// Dispatch commands specified on the command line
if (!ProcessShellCommand(cmdInfo))
return FALSE;
*/

// The main window has been initialized, so show and update it.
pMainFrame->ShowWindow(SW_SHOWMAXIMIZED);
pMainFrame->UpdateWindow();

return TRUE;
}


在MainFrame.cpp文件中的以下位置有以下代码：

在此打开一个多文档模板的一个实例，如何让它只能出一个窗口，不能多于一个窗口呢？
void CMainFrame::OnCxmx() //和菜单相关联
{
// TODO: Add your command handler code here
//查询明细
CFrameWnd* pNewFrame = (theApp.pCxmxDocTemplate)->CreateNewFrame(NULL, NULL);
if (pNewFrame == NULL)
return ;

(theApp.pCxmxDocTemplate)->InitialUpdateFrame(pNewFrame, NULL);
return;
}

[laozhuang]

Laozhuang 我的Email:[e-mail]，先谢谢各位！！！！

[蒋晟]

CDocTemplate::GetFirstDocumentPosition
CDocTemplate::GetNextDocument

[蒋晟]

search GetFirstDocumentPosition in MSDN

[laozhuang]

请问jiangsheng具体怎么调用应该加在哪个地方？是在声明的时候加入GetFirstDocumentPosition()?还是其它地方？
请帮我指明，好吗？谢谢！