title: Only update field in mongodb if it is smaller than another field
body: <p>I currently have the following query:</p>
  
  <pre><code>Meteor.users.update({energy: {$lt: 30}}, {$inc: {"energy": 1}}, {multi: true});
  </code></pre>
  
  <p>But I want to do the following:</p>
  
  <pre><code>Meteor.users.update({energy: {$lt: maxenergy}}, {$inc: {"energy": 1}}, {{multi: true});
  </code></pre>
  
  <p>Where maxenergy is another field in the document, is this possible or do I need to loop over the entire collection to do this?</p>
  
  <p>Any help would be appreciated.</p>