title: jQuery validate only if a specific radio button is selected
body: <p>I got stuck at a particular situation</p>
  
  <p>I have 2 radio buttons</p>
  
  <pre><code>&lt;input type="radio" value="YES" id="sub" name="sub"&gt;Yes
  &lt;input type="radio" value="NO" id="sub" name="sub"&gt;No
  </code></pre>
  
  <p>When, Yes is selected, I need to validated 1 text-field</p>
  
  <pre><code>&lt;input type="text" id="price" name="price" /&gt;
  </code></pre>
  
  <p>I am using jQuery validation plug-in</p>
  
  <p>Please help me with this, Thanks.</p>