title: Read the calculated values from Excel using AddIn Formulas and Microsoft Object Library
body: <p>we are trying to retrieve a calculated value from a cell which has add-In formulas in it.
  The sample add-in "myUtilityl.xla" is working properly in excel. It retrieves value for the addin function <code>=ISOWEEKNUM(F9)</code>. But we are unable to retrieve the value programatically using C# &amp; Microsoft Object Library. The add-In "myUtilityl.xla" is attached to Excel. Environment is VS2010</p>
  
  <p>I am providing the sample code here.</p>
  
  <pre><code>        string path = @"C:\Test.xls";
          Workbook theWorkbook;
          Worksheet theWorksheet;
          Range readRange;
          Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();            
          theWorkbook = app.Workbooks.Open(path);
          Sheets theSheets = (Sheets)theWorkbook.Worksheets;
          theWorksheet =  (Worksheet)theWorkbook.Worksheets.get_Item("Sheet1");            
          readRange = theWorksheet.get_Range("B1");            
          MessageBox.Show(Convert.ToString(readRange.Value));
          //theWorkbook.Save();
          app.Workbooks.Close();
  </code></pre>
  
  <p>I am new to Microsoft Object library. Any help or clue will be very helpful.</p>