Import threads from other systems

We've been using WebWiz 9.x for about a year now and it's working out well.  We've added a group that had another forum software system and need to try to import their threads/posts into our setup.   I've use the import users function a few times.  Is there something similar available for importing threads/posts?   We're using the MS Access database version and we think we can make sense of the various tables in the WebWiz MDB database.   Before we started playing and see if we can import their threads/post from their system thought I'd ask here and see if anyone had been down this road before or if there were any tools already available.   Like the user import function, we could probably get the various threads from their existing system into another MDB Access file.  Then it would be builting a routine to add them into the various tables in the WebWiz database.

I managed to do it for PHPBB3 to Webwiz 9.x but it was really hard, I tried to write it so it could work as a script for anyone to use, but that made it even harder so I just wrote it for our needs.  Takes around 3-4 hours to run for ~80k messages and 3k users which I think is down to the hardware constraints of SQL Server Express (I should probably just buy the dev edition).