outlook express restore single folder

A user deleted a folder, had to be recovered using an "unerase" type utility.
I have the recovered dbx file. But now Outlook Express is very uncooperative in letting me import this single folder. Or add it back to the mailstore and have it seen and included by Folders.dbx presumably. What's the trick?
When I try to import it, and point to the folder where the dbx file is, it reports no messages found.
Something else with adding it to Folders.dbx somehow?
This certainly "should" be easier.
Anyone else jumped through this set of hoops before?
Thanks