Biff,

my congratulations also on a mammoth effort!

My interpretation of the OP's original request was that he wanted one
result - I had imagined that he had one massive lookup table (of 393000
rows) which had to be split into 6 because of Excel's row limit of 64k.
If this were the case, I'm not sure if he (or you or Max) ensured that
there were no duplicates between the sheets.

Very interesting - well done!

Pete