Routes Parameter manipulation

I am creating a new site to replace an existing one and want to
preserve urls that people have bookmarked and appear in search
engines. My solution to this is create a route that takes a historical
url and pass that along to the controller of my choice with a new id
that was looked up in a table. This seems to work in theory but I am
stuck on something.

Here is my approach:

I want to take the url: /category/123
lookup 123 in a table which will return a new id for my new catalog.
and send the user to a different controller with id 456 (or whatever
the looked up value is)

I have a method that is called in the route and will return a value.
The problem is passing the supplied id (named :cid in my code below).
I can't seem to pass the value that is in the url. Everything else
works. I can hard code the parameter to the catmap method and the
route works.


  def catmap(cat)

    list ={'60'=>'2','61'=>'3'}

    return list(cat)

class ApplicationController < ActionController::Base
  map.connect 'category/:cid',:controller => 'list', :action =>
'model', :id =>catmap(cid)