select a child element in jquery object
<p>I'm new to jquery and I have a basic question now.</p>

<p>I have a jquery object got from a jquery selector. e.g</p>

<pre><code>var obj = $('#certainTR');
</code></pre>

<p>Now, I want to get the element in this  object and I cannot use '#certainTR > date' in a selector because '#certain' is not passed in my subroutine. Is there anyway to make a selection base on a object? Thanks a lot in advance!</p>
