it took me a few months to get this working and I've bugged people here onthe list to help me out - it's finally working!
I have a patch that generates the coefficients for [cpole~] according to the [vcf~]'s inputs and I was able to draw a freq response according to the cpole's z-transform.
it wasn't easy - I had help of a friend understanding the source code of vcf~ and in tjis forum someone solved all the z-transform issues for me. http://dsp.stackexchange.com/questions/17917/real-and-imaginary-frequency-re...
well, here's the patch for anyone who cares understanding vcf better. The patch is a mess and very dirty, but I will clean it up and put it in my computer music course examples soon.
cheers