title: Concat rails variable inside Excel XML View
body: <pre><code>&lt;Cell ss:MergeDown="1" ss:StyleID="ce20" ss:Formula=&lt;%= "of:=SUM([.G7:.G#{@nb_days}])" %&gt;&gt;&lt;Data ss:Type="Number"&gt;&lt;/Data&gt;&lt;/Cell&gt;
  </code></pre>
  
  <p>I'm trying to create this formula using my variable <code>@nb_days</code>. It contains a number, such as 31. I've tried several ways but it doesn't work. Either I got a "General output error" at the file opening or the formula is displayed in the cell.</p>
  
  <p>How could I concat the string with the variable?</p>