Can I flush the event stack within Firefox using Javascript?

Question

I have a hierarchy of tags within my HTML which all contain onclick event handlers. The onclick is pushed onto the event stack from the leaf back through the root of the hierarchy. I only want to respond to the leaf onclick event. Can I flush the event stack rather than using a flag?

For instance:

    <ul>
      <li onclick="nada('1');"><a href="#1">1</a></li>
      <li onclick="nada('2');"><a href="#2">2</a>
        <ul>
          <li onclick="nada('2.1');"><a href="#2.1">2.1</a></li>
          <li onclick="nada('2.2');"><a href="#2.2">2.2</a></li>
          <li onclick="nada('2.3');"><a href="#2.3">2.3</a></li>
        </ul>
      </li>
      <li onclick="nada('4');"><a href="#4">4</a></li>
      <li onclick="nada('5');"><a href="#5">5</a></li>
    </ul>

Clicking on 2.2 using this function...

function nada(which)
  {
  alert(which);
  }

...will result in two alerts for '2.2' and '2'.

What could I add to the nada function to eliminate the alert for '2'?