I understand what you did Dave, but I still don't understand why you had a problem in the first place. Normally, unless you've changed something on your end, if you delete a post the B_Number doesn't get used again.
On my board, I can add an event, say number 123, delete it, then post a new event, and the new post number is 124 - there is no 123 any more.
This makes sense - otherwise, if you had a link to a post from somewhere, that link could pull up a different post altogether (if there was a delete/add in the meantime).
So there's something else happening on your boards, that's causing B_Number to get re-used. That's not good I think, I can't think of the exact scenarios that would result in bugs but I know that they must be there.
Max