Actually Rod I considered that but discarded it.
Not because it can't be made to work, but because it was apparent it was not what he wanted; it's only an approximation. And yes it would be pokey. Not sure how big his library is.
There are other approximations that could be done, as I suggested in previous posts, that are also based on the dates of the files. Any of those other approaches would run much faster, and would be easier to execute.
What I was getting at earlier, when I mentioned create a new field, was that since the creation dates on folders don't change, there is no need to worry about dynamically reading them. So he could enter the appropriate folder dates in to a new field (applied to the files in that folder) and then by sorting on that field he would get the exact same results as he did in explorer. But of course that is manual data entry.
Everything else that can be done, both the other things I thought of, and what you mentioned Rod, are all approximations that just produce merely similar results. I wasn't particularly happy with any of them, and didn't think he was either. And he didn't bite at any of those ideas I mentioned, so...
Like I said, the actual point or benefit of sorting by folder creation date completely eludes me. Sorting by folder modification date is great, because it indicates folders that have new files. But created date is pointless; I can only see value if folders are constantly being created and destroyed (as by an automated process) but such folders wouldn't be part of a functional MC library, as there would be constant broken links, (unless you have auto import running with fix broken links=yes, which is dangerous). So I just don't get it. But to each his own.