title: How to disable button If I select NO in dropdown list
body: <p>The code is simply like this:</p>
  
  <pre><code>&lt;select id="productextra[@count@]"&gt;
  &lt;option value="[@option_id@]"&gt;Yes&lt;/option&gt;
  &lt;option value="[@option_id@]"&gt;No&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>The button should be disable is:
  Add to cart</p>