Extracting addresses of bounced mail

So, my shiny mailing list is running great under procmail, but
there is one more thing I would like to be able to do.

When mail bounces back to me, I want to extract the bad account
name so that I can automagically remove that person from the list.

Does anyone have anything like this written up already?  And no, in
case you are wondering, I am not using SmartList.  

Thanks for any help.

Pete McNab