title: Adding a value to a variable in Django templates
body: <p>This is a very quick question, which I think may be a limitation in the templates.</p>
  
  <p>I'm adding a value to a variable in a template using the |add:"num" feature, I'm trying to use another variable as the number but it doesn't seem to work.  Should this be possible ? </p>
  
  <p>e.g.</p>
  
  <pre><code>{{ pagecontrol.start_page|add:"-pagecontrol.news_per_page" }}
  </code></pre>
  
  <p>Thanks in advance all.</p>
  
  <p>Wayne</p>