If you run BP in offline mode on the DMZ computer, you can schedule it ‘Download available updates’. It will download the Microsoft offline scan file, and then it will download the updates that are available for the computer that initiated the download to its local cache. It will not download the entire updates repository– it will only download the updates that are available for the computer that initiated the download, based on the filters/settings that you have specified in ‘Tools > Settings > Windows update’. There is not currently any way to schedule the download of the entire offline updates repository.
-Doug