Find an xml node from a session variable?

Can anyone point me to a tutorial or sample on how to find a specific
node in an xml file based on a session variable.

What I want to do is display content to a user based on their user id
that is set or stored in a session variable.

For instance if a user logs in and a session variable gets set to
"joeuser" I want to search an xml document for the node that has
joeuser's data in it and display just the fields under his/her node.

The parser is msxml version 6 I believe but I would like to keep the
code as os/server agnostic as possible.

Also, can I do this with javascript? I would really like to use one of
the nice javascript libraries like yui or mootools or prototype etc...

--
Kind Regards,
Mike