Conditional Format to highlight differances between to sets of data

[Mctabish]

Over the last umpteen years, I have had several crashes of outlook,
re-entered data, cleaned and re imported data...
The gist is I have many THOUSANDS and THOUSANDS of contacts that need to be
cleaned and purged. I have tried various solutions for Outlooks, but I still
have not got the lists down to a managemble size due to all of the differant
variations and enties of these contacts.

What I am wanting to do is to have 2 "lists", one (columns A - CN - standard
mapping export from outlook, then 3 columns used to generate "keys") I then
use a duplicate set of columns (DA-QQ, again, the sameset of columns)

The first set is the UNCLEANED, the second set is the CLEANED data.
What I would LIKE to do is something similar to this:

Using the KEY for list set 1, do a MATCH into the KEY for set 2, and then if
the data is found, then compare each item column by column, with the item of
the row returned by match, and if that cell of data is different, then
highlight it.

I am SURE this can be done, but for the life of me, I have been going crazy

Could somebody give me some pointers?

Thanks
Mc