Sync Exch/Groupwise Global Address books

We need to have an Exchnage server 5.5 global address book auto sync with a Groupwise 5.5 global address book over a standard internet connection.

We know that it can be done via a VPN but do not have a VPN in place. It can also be done by setting up Groupwise at the Exchange site but this site has no Groupwise skill so is not a viable answer.

The amount of data requried to be transferred is irrelevant as both systems have DSL connections to the internet.

Is there a mechanism that can be setup up to provide an auto sync process?? It would be great if the process works both ways as theree is a need to have the Groupwise address book details update the Exchange server as well!