How to recognize the difference among Excel 97 files, Excel 2000 files, and Excel 2002 files by using Visual C++ 6.0

    int IsExcel9(WCHAR *wcFilename) {

        // Open document as an OLE compound document...
        HRESULT hr;
        IStorage *pStg = 0;
        hr = ::StgOpenStorage(wcFilename, 0, STGM_READWRITE | STGM_SHARE_EXCLUSIVE, 0, 0, &pStg);
        if(FAILED(hr)) return 0;
    
        // Now, get the Workbook stream
        IStream *pStm;
        WCHAR *wcBookStm = L"Workbook";
        hr = pStg->OpenStream(wcBookStm, 0, STGM_READWRITE | STGM_SHARE_EXCLUSIVE , 0, &pStm);

        if(FAILED(hr)) {
            pStg->Release();
            return 0;
        }

        char buf[32000];
        DWORD dwRead;
        short id, len;

        for(;;) {
            // Read id & len first...
            HRESULT hr = pStm->Read(&id, 2, &dwRead);
            if( (FAILED(hr)) || (dwRead != 2) ) break;
            pStm->Read(&len, 2, &dwRead);
            if(dwRead != 2) break;
            if((id == 0) && (len == 0)) break;

            // Check for XL9File record
            if(id == 0x1c0) {
                pStm->Release();
                pStg->Release();
                return 1;
            }

            // Eat record...
            if(len > 32000) len = 32000;
            pStm->Read(buf, (long)len, &dwRead);
            if((DWORD)len != dwRead) break;
        }

        // Cleanup
        pStm->Release();
        pStg->Release();
    
        return 0;
    }