Ошибка COM (Excel) без использования MFC, ATL

HRESULT xls_tuned::AutoWrap(int autoType, VARIANT *pvResult, IDispatch *pDisp, LPOLESTR ptName, int cArgs...) {
    // Begin variable-argument list...
    va_list marker;
    va_start(marker, cArgs);
 
    if(!pDisp) {
        ::MessageBox(NULL, "NULL IDispatch passed to AutoWrap()", "Error", 0x10010);
        exit(0);
    }
 
    // Variables used...
    DISPPARAMS dp = { NULL, NULL, 0, 0 };
    DISPID dispidNamed = DISPID_PROPERTYPUT;
    DISPID dispID;
    HRESULT hr;
    char buf[200];
    char szName[200];
    strcpy(buf,(char*)ptName);
 
    // Convert down to ANSI
    WideCharToMultiByte(CP_ACP, 0, ptName, -1, szName, 256, NULL, NULL);
 
    // Get DISPID for name passed...
    hr = pDisp->GetIDsOfNames(IID_NULL, &ptName, 1, LOCALE_USER_DEFAULT, &dispID);
    if(FAILED(hr)) {
        sprintf(buf, "IDispatch::GetIDsOfNames(\"%s\") failed w/err 0x%08lx", szName, hr);
        ::MessageBox(NULL, buf, "AutoWrap()", 0x10010);
        exit(0);
        return hr;
    }
 
    // Allocate memory for arguments...
    VARIANT *pArgs = new VARIANT[cArgs+1];
    // Extract arguments...
    for(int i=0; i<cArgs; i++) {
        pArgs[i] = va_arg(marker, VARIANT);
    }
 
    // Build DISPPARAMS
    dp.cArgs = cArgs;
    dp.rgvarg = pArgs;
 
    // Handle special-case for property-puts!
    if(autoType & DISPATCH_PROPERTYPUT) {
        dp.cNamedArgs = 1;
        dp.rgdispidNamedArgs = &dispidNamed;
    }
 
    // Make the call!
    hr = pDisp->Invoke(dispID, IID_NULL, LOCALE_SYSTEM_DEFAULT, autoType, &dp, pvResult, NULL, NULL);
    if(FAILED(hr)) {
        sprintf(buf, "IDispatch::Invoke(\"%s\"=%08lx) failed w/err 0x%08lx", szName, dispID, hr);
        ::MessageBox(NULL, buf, "AutoWrap()", 0x10010);
        exit(0);
        return hr;
    }
    // End variable-argument section...
    va_end(marker);
    delete [] pArgs;
 
    return hr;
}

// Constructor
xls_tuned::xls_tuned(bool visible)
{
 
    pXlApp = pXlBooks = pXlBook = pXlSheet = pXlRange = 0;
    for(int i = 0;i<5;i++) IDispatch_pointers[i]=0;
 
    // Initialize COM for this thread...
   CoInitialize(NULL);
 
   // Get CLSID for our server...
   hr = CLSIDFromProgID(L"Excel.Application", &clsid);
 
   if(FAILED(hr)) {
      //::MessageBox(NULL, "CLSIDFromProgID() failed", "Error", 0x10010);
   }
 
   // Start server and get IDispatch...
 
   hr = CoCreateInstance(clsid, NULL, CLSCTX_LOCAL_SERVER, IID_IDispatch, (void **)&pXlApp);
   if(FAILED(hr)) {
      //::MessageBox(NULL, "Excel not registered properly", "Error", 0x10010);
   }
 
   // Make it visible (i.e. app.visible = 1)
   {
 
      VARIANT x;
      x.vt = VT_I4;
      x.lVal = visible;
      AutoWrap(DISPATCH_PROPERTYPUT, NULL, pXlApp, L"Visible", 1, x);
      IDispatch_pointers[0] = 1;
   }
}

// Activate Workbooks function
int xls_tuned::Workbooks()
{
    // Get Workbooks collection
   {
      VARIANT result;
      VariantInit(&result);
      AutoWrap(DISPATCH_PROPERTYGET, &result, pXlApp, L"Workbooks", 0);
      pXlBooks = result.pdispVal;
      IDispatch_pointers[1] = 1;
   }
   return 0;
}
 
// Add new workbook
int xls_tuned::Addworkbook()
{
    // Call Workbooks.Add() to get a new workbook...
   {
      VARIANT result;
      VariantInit(&result);
      AutoWrap(DISPATCH_PROPERTYGET, &result, pXlBooks, L"Add", 0);
      pXlBook = result.pdispVal;
      IDispatch_pointers[2] = 1;
   }
   return 0;
}
 
// Open local file
int xls_tuned::Open(std::string filename)
{
    // Call Workbooks.Add() to get a new workbook...
   {
      LPOLESTR pszFileNameW;
      AnsiToUnicode(filename.c_str(), &pszFileNameW);
 
      VARIANT parm;
      parm.vt = VT_BSTR;
      parm.bstrVal = ::SysAllocString(pszFileNameW);
 
      VARIANT result;
      VariantInit(&result);
      AutoWrap(DISPATCH_PROPERTYGET, &result, pXlBooks, L"Open", 1, parm);
      pXlBook = result.pdispVal;
      CoTaskMemFree(pszFileNameW);
      IDispatch_pointers[2] = 1;
   }
   return 0;
}

int xls_tuned::Range(std::string range_sel)
{
    // Get Range object for the Range A1:O15...
 
    LPOLESTR pszRangeW;
    AnsiToUnicode(range_sel.c_str(), &pszRangeW);
 
    VARIANT parm;
    parm.vt = VT_BSTR;
    parm.bstrVal = SysAllocString(pszRangeW);
    //::MessageBox(NULL, (CHAR *) pszRangeW, "Notice", 0x10000);
 
    VARIANT result;
    VariantInit(&result);
    AutoWrap(DISPATCH_PROPERTYGET, &result, pXlSheet, L"Range", 1, parm);
    VariantClear(&parm);
 
    pXlRange = result.pdispVal;
    CoTaskMemFree(pszRangeW);
    IDispatch_pointers[4] = 1;
}
 
int xls_tuned::Write2Range(VARIANT data)
{
    // Set range with our safearray...
   AutoWrap(DISPATCH_PROPERTYPUT, NULL, pXlRange, L"Value", 1, data);
}

//Activate sheet
int xls_tuned::Activatesheet(int sheet)
{
    // Get ActiveSheet object
 
    VARIANT x;
      x.vt = VT_I4;
      x.lVal = sheet;
 
      {
      VARIANT result;
      VariantInit(&result);
   if (sheet) {
        AutoWrap(DISPATCH_PROPERTYGET, &result, pXlBook, L"Sheets", 1, x);
        pXlSheet = result.pdispVal;
        AutoWrap(DISPATCH_PROPERTYPUT, NULL, pXlSheet, L"Activate", NULL);
        //pXlSheet = result.pdispVal;
      } else {
    AutoWrap(DISPATCH_PROPERTYGET, &result, pXlApp, L"ActiveSheet", 0);
        pXlSheet = result.pdispVal;
      }
      IDispatch_pointers[3] = 1;
   }
   return 0;
}