Hi Alan
That would be great, I hope you find a solution that's not too expensive/time consuming. One thing that confuses me about the Z21 and train detection is that when using the loconet there are detectors that you can use such as the uhlenbrock but I believe, but may well be wrong, that the digitrax bdl 168 is not suitable (I liked this as it had 16 sections). I know you are using Reed switches for your layout but I was thinking of using the current detection root as my electrics aren't the best!
Cheers
Alan