MFC对话框程序只能同时运行一个

        HANDLE m_hMutex; //用于互斥的对象句柄;
	m_hMutex = ::CreateMutex(NULL, TRUE, L"hc_comra");
	if (GetLastError() == ERROR_ALREADY_EXISTS) //程序已经运行;
	{
		HWND   oldHWnd = NULL;   
		oldHWnd = ::FindWindow(NULL, _T("COMRA")); //查找已经运行的程序;
		if (oldHWnd)   
		{   
			::ShowWindow(oldHWnd, SW_SHOWNORMAL); //激活显示找到的已运行的程序;
			::SetForegroundWindow(oldHWnd);       //将已运行的程序设置为当前窗口;
		}  
		CloseHandle(m_hMutex);
		m_hMutex = NULL;
		return FALSE;
	}        HANDLE m_hMutex; //用于互斥的对象句柄;
	m_hMutex