[xsl] Selecting only those nodes whos attibutes contain a given substring

[Peter Hickman <peter@xxxxxxxxxxxxx>]

I am having to write some XSLT that needs to decide if it needs to 
recurse into the contents of the current mode. Basically I am at a node 
and I only want to recurse into it if at least one of the child nodes 
has an attribute called "class" who's value contains the sub string 
"menublock-selected-". Otherwise I am going to skip this node.

The XML is part of an open source project so there is little chance of 
patching it up.

Any ideas?