How to select elements from a set that are children of another element
<p>The title is a bit confusing but here's what I'm after:</p>

<ul>
<li><p>I have a set of elements containing all the <code>h3</code> elements in a page.<br>
In jQuery terms: <code>var mySet = $('h3')</code>.</p></li>
<li><p>I also have an div element <code>var myContainer = $('div#foo')</code></p></li>
<li><p>I need to find all items in the set <code>mySet</code> that are children of <code>myContainer</code>.</p></li>
</ul>

<p>Any ideas? I bet there's some magical one liner for this but I cannot think of any. I'd rather <em>not</em> loop through every element in the set manually and use <code>.closest(myContainer)</code> or something like that to determine the relationship.</p>

<p>Note that in my scenario, I cannot use a new selector like <code>$('div#foo h3')</code> (that would be too easy) as I don't have access to the actual selector values. So it has to be dynamic.</p>
