title: LibXL: excel cross-sheet formulas not updated
body: <p>I'm dealing with a problem with <code>libXL</code> and <em>Office365</em>.
  I created an Excel file with <em>Office 365</em>: a simple formula which shows the content of a cell from another sheet. Then I proceeded to write something in that source cell through <code>libXl</code>. When I open the output file the formula is not calculated until I press <code>CTRL+ALT+SHIFT+F9</code>.</p>
  <p>If I create the <code>xlsx</code> file from <em>Office 2013</em> then the formula is correctly updated.</p>
  <p>Couldn' find anything on their website whether <code>O365</code> is supported or not.</p>
  <p>Here's the code to reproduce the issue, (I can provide the two input xlsx files if needed):</p>
  <pre><code>#include &quot;stdafx.h&quot;
  #include &quot;libxl.h&quot;
  
  using namespace libxl;
  
  int main()
  {   
      Book* book = xlCreateXMLBook();
  
      // xlsx file created by Office 2013
      if (book-&gt;load(L&quot;office2013.xlsx&quot;))
      {
          Sheet* sheet = book-&gt;getSheet(0);
          if (sheet)
              sheet-&gt;writeNum(2, 2, 42);
  
          book-&gt;save(L&quot;okay.xlsx&quot;); // works correctly when opened
      }
  
      // xlsx file created by O365
      if (book-&gt;load(L&quot;office365.xlsx&quot;))
      {
          Sheet* sheet = book-&gt;getSheet(0);
          if (sheet)
              sheet-&gt;writeNum(2, 2, 42);
  
          book-&gt;save(L&quot;bugged.xlsx&quot;); // must press CTRL+ALT+SHIFT+F9 to see '42' in the second sheet
      }
      
      book-&gt;release();
      
      return 0;
  }
  </code></pre>
  <p>This is the source sheet (number 42 written by the above code): <a href="https://i.stack.imgur.com/hp7Ti.png" rel="noreferrer">https://i.stack.imgur.com/hp7Ti.png</a></p>
  <p>This is the not working formula (written in Excel): <a href="https://i.stack.imgur.com/BhGW2.png" rel="noreferrer">https://i.stack.imgur.com/BhGW2.png</a></p>
  <p>Thank you</p>