More tokens in URL field

My customer is using Coremetrics tracking and needs additional information about who is clicking back to the site through RSS feeds. They want to do this by adding an additional query string to the URL. I would have no problem doing this except that they want part of that query string to be taken from the taxonomy term (actually supplied by the Term Fields module). How can we do this? The only tokens shown are [title] and [nid]. I have a custom module that is already supplying a couple of extra tokens elsewhere, so adding my own tokens is not a problem.