No problem. Post again if you have any problems.
Just in case you haven't found it already, there's a semi-helpful explanation of how to drive datamanagers here:
http://www.vbulletin.com/docs/html/data_managers
... and the generic auto-generated API docs are here:
http://members.vbulletin.com/api/
I'd advise doing this as an AdminCP "maintenance task". Plenty of example code to borrow for building the scaffolding for batched tasks like this.
-- hugh