document.evaluate

Hi,

I have a page with a couple of XML islands. I call the following code to 
return a specific node in one of the XML islands
    document.evaluate(cXPathString, xNode, oNSResolver, 
XPathResult.FIRST_ORDERED_NODE_TYPE, null);
where xNode is a reference to the XML island I want to query. However, my 
result is always in context of the first XML island on the form

Is this a bug or am I doing something wrong?

Thanks