Test for value of childnote

Hi everybody

I would like to create a "status field" on our intranet to display the status of the IT systems in our org.

I wolud like to display the status from an RSS feed we use for general news from the IT department.

The feed could look something like this:

 <?xml version="1.0" encoding="UTF-8"?>
 <?xml-stylesheet type="text/xsl" href=[link=http://somewhere.com/somestylesheet.xsl]http://somewhere.com/somestylesheet.xsl[/link] version="1.0"?>
 <rss version="2.0">
 <channel>
      <title>Test RSS feed</title>
      <description>Feed to test &quot;traffic light&quot;</description>
      <link>http://www.testfeed.xml</link>
      <language> da</language>
      <lastBuildDate>Mon, 30 Jul 2007 12:23:51 +0200</lastBuildDate>
      <pubDate>Mon, 30 Jul 2007 12:23:47 +0200</pubDate>
      <generator>FeedForAll v2.0 (2.0.2.8)</generator>
      <item>
          <title>Entry three</title>
          <description>The third entry</description>
          <category domain="">Critical</category>
           <pubDate>Mon, 30 Jul 2007 12:21:38 +0200</pubDate>
      </item>
      <item>
          <title>Entry two</title>
          <description>The second entry</description>
          <pubDate>Mon, 30 Jul 2007 12:21:16 +0200</pubDate>
      </item>
      <item>
          <title>Entry one</title>
          <description>The first entry</description>
          <pubDate>Mon, 30 Jul 2007 12:19:09 +0200</pubDate>
      </item>
 </channel>
 </rss>
 

I would like to have a "traffic light" on the Intranet that changes to red if a category node with "Critical" is present, yellow if the category node contains "Problem", and green if no category node is present. (three different .gif's)
I know I have to check the node and then act on behalf of the result and display the traffic light with the right color, but what is the easiest way to do this ?
Unfortunatlly I cant figur out how to achive this. Hopefully someone here are able to help.

What have you tried so far? Basicly you would want to do an XPath query to see if there are any nodes that meet your criteria.

I'm all new to XML/XSL(T), but I have played around a little.
 
The XML file is genereted using a RSS feed editor and I have added a style sheet (XSL)
I use this xsl to display the feed on the Intranet.
 
Now I want to use the same feed to change an icon in an iframe.
How do I get the If... Then logic on the result I get from the query ? 
Can I do an XPath query from HTML, or can I somehow use several style sheets on the same XML source ?
 
- Søren