Hello,
I have performed a number of similar tasks in the past for various employers, so this sounds right up my street!
Combining different mdb files can be done relatively quickly as long as the tables have the same data structure. If not, I would first need to analyse the data, and then confirm with yourself as to how you'd like it merged. All this could be done without using VBA.
I may need some more clarity when you say "select records every 10 records from the combined one". If you mean export every 10 records into excel (or another file format) that can be done, or if you want to be able to cycle every 10 records in an Access userform, this is possible as well.
I look forward to the opportunity to work with you.
Regards
Russell