GetActiveObject to get pDTE when multiple instances started (C++)

Hi!

I'm trying to get DTE object of instance of MS Visual Studio 2010. When there are only one instance I can use this code:

CLSID clsid = {0};
HRESULT res = ::CLSIDFromProgID(L"VisualStudio.DTE.10.0", &clsid);
IUnknownPtr pUnk;
GetActiveObject(clsid, NULL, &pUnk);
_DTEPtr pDTE = pUnk;

But when there are multiple instances of MSVS, it gets DTE of first instance. How can I get table of all running instances and select which DTE to get (I must use C++)?

Sorry for my bad English.