Menu en Javascript

[safe]

te referis a algo asi?

Código:

<form name="form1" method="post" action="">
  <select id="menu" disabled>
    <option value="1">1</option>
    <option value="2">2</option>
  </select>
  <select name="combo" multiple onChange="document.getElementById('menu').disabled=false">
    <option value="1">1</option>
    <option value="2">2</option>
  </select>
</form>