find TR by class inside div

find TR by class inside div

Hello Guys,
I am creating a user control which would exist multiple times on a page.
I am wrapping this user control inside a div so the id and name is unique.
Inside this, I want to add/remove/update controls.
here is pseudo code:
<div id="mydiv" runat="server">
<table id="tbl1">
<tr class="myTestRowClass">
<td> 1 </td>
<td> 2 </td>
</tr>
</table>
<input type="button" onclick="javascript:return GetRowByClass(this);" text="Click me" />
</div>


in the javascript method is where I need help:
function GetRowByClass(sender){
var parentDivOfSender = sender.parentNode;
parentDivOfSender.HOW_SHOULD_I_FIND_myTestRowClass ???
}[/b]