title: Changing 'top' property at runtime in Flex
body: <p>In the follow Canvas, how do I change the property <strong>top</strong> at runtime?</p>
  
  <pre><code>&lt;canvas top="10"/&gt;
  </code></pre>
  
  <p>I tried:</p>
  
  <pre><code>&lt;canvas top="{ topVariable }"/&gt;
  </code></pre>
  
  <p>But the binding doesn't seem to take effect. How can this be achieved?</p>