Here's a simple example to give you an idea. Edit the bottom shape (drag, rotate, node-edit) and the top one will respond. As you see there is some support in the program already, but it's quite buggy. Hopefully it can be cleaned up and made usable. (You could help, too, given that you need it for your designs :)

_________________________________________________________________ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus&pgmarket=en-ca&RU=http%3a%2...