title: Excel Adds "@" Sign Into Formula Created by XLSXWriter?
body: <p>In XLSXWriter, I'm using the following code to add a formula to a workbook:</p>
  
  <pre><code>worksheet.write_formula(row, col, '=MAX(IF(AL3:AL7&lt;=$AI$8,AL3:AL7))')
  </code></pre>
  
  <p>When I open the workbook in Excel, it has an "@" sign inserted into it, and throws a "#VALUE!" error. </p>
  
  <pre><code>=MAX(IF(@AL3:AL7&lt;=$AI$8,AL3:AL7))
  </code></pre>
  
  <p>How can I correct this?</p>