Coldfusion dynamic redirection

I am trying to redirect based on url.  So if someone enters www.mydomain/something, I want to pull the "something" portion of the url and query a database for that and redirect to the associated url. I have tried doing this in both the application file and in a custom 404 error file. I think that beause the directory something does not really exist the getwebpath function is not working in the application file and once it bounces to the error page it is still not picking up the directory.