title: Open excel workbook but set calculations to manual
body: <p>I have tried a few options but none seem to work, and some send errors.</p>
  
  <p>Please let me know what I am doing wrong</p>
  
  <pre><code>public string Main(String wbPath, String wbName)
  {
      string cName = "";
      Excel.Application xlApp;
      Excel.Workbook xlWB;
      Excel.Worksheet xlWS;
  
  
      xlApp = new Excel.Application();
      xlApp.DisplayAlerts = false;
      xlApp.Calculation = Excel.XlCalculation.xlCalculationManual;       //Error occurs here 
  
      xlWB = xlApp.Workbooks.Open(wbPath + wbName);
  
      xlWB.SaveAs("vFile.html", Microsoft.Office.Interop.Excel.XlFileFormat.xlHtml);
      cName = xlWB.FullName;
      xlWB.Close();
  
  
      xlApp.Quit();
  
      return cName;
  }
  </code></pre>
  
  <p>Error code:</p>
  
  <pre><code>{"Exception from HRESULT: 0x800A03EC"}
  </code></pre>