Oh, you really did mean "share" in the complete sense. I'm inclined to think you're right, that if you want updates to be placed in B even while people are using B, you'd have to make it a database. It doesn't have to be Access—I mean, it could be Oracle or whatever—but you probably can't do that in Excel. Excel complains about just two people trying to have write access to the same workbook, much less 12.

Now, if you're really in love with the idea of doing it in Excel, then there are probably ways to get fairly quick updates. Any changes could be written to a file, and then as soon as the workbook is free—not being updated by anyone—a program could run that would load the changes into the workbook, so they'd be available to the next person who opened it. I'm not sure how that would be done, but I can think of a couple possibilities. But it wouldn't be true concurrent sharing. It's the best I know how to do, though. Sound interesting?