Loading Child Nodes Dynamically?

[cowsdonthack]

[This is a rewording of a previous post here, only more concise for those who tl;dr]
http://www.codingforums.com/showthread.php?t=177257

So, what I need to do is I need to display all the Options <OPT> of a product <PR> whenever it's selected

How do you load all the Options <OPT> but only for each product <PR>?

JS
oldTextAry = new Array();
var xmlDoc;
if (window.XMLHttpRequest) {
xmlDoc=new window.XMLHttpRequest();
xmlDoc.open("GET","data.xml",false);
xmlDoc.send("");
xmlDoc=xmlDoc.responseXML;
}
else if (ActiveXObject("Microsoft.XMLDOM")) {
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false; xmlDoc.load("data.xml");
}
var x=xmlDoc.getElementsByTagName("PR");i=0;XML
<PRODUCT>
<PR>
<TITLE>1E Series Cylinders - 1E2 Rim Cylinder</TITLE>
<IMG>http://www.asdf.com/images/cache/asdf.com-dc8ca9ef266a32a6fc42c80fbd39eb77.jpg</IMG>
<ENL>http://www.asdf.com/images/cache/asdf.com-b21e748612010de9b9c722fd474419d4.jpg</ENL>
<LINK> </LINK>
<INFO> </INFO>
<OPTION>
<OPT>1</OPT>
<OPT>2</OPT>
<OPT>3</OPT>
<OPT>4</OPT>
<OPT>5</OPT>
</OPTION>
</PR>
<PR>
<TITLE>1E6 Tapered Mortise Cylinder</TITLE>
<IMG>http://www.asdf.com/images/cache/asdf.com-9cb55aa0848d4c3fdd53b3600a6d8eb3.jpg</IMG>
<ENL>http://www.asdf.com/images/cache/asdf.com-d92d734b54b185fa6bd551673a3d63af.jpg</ENL>
<LINK> </LINK>
<INFO> </INFO>
<OPTION>
<OPT>3</OPT>
<OPT>4</OPT>
<OPT>5</OPT>
<OPT>8</OPT>
<OPT>3</OPT>
</OPTION>
</PR>
</PRODUCT>