Incremental CD set

[Stefan Karrmann <sk@mathematik.uni-ulm.de>]

Is there a method to extend a given CD set incremental?

E.g. I've the 4 CD set of Debian GNU/Linux 2.1 (slink) and one
additional CD. Now, I want to get the actual potato packages for i386
and hurd. As there are a lot of symlinks from potato to slink, I only
need the new packages not a complete potato CD set. If I provide the
Packages.cd files of the last CD (CD5 or CD2) and the new Packages files it
is possible to choose the packages for the next CDs. Their Packages.cd
files can be created then, too. 

Any ideas for such a method?
-- 
Stefan Karrmann