Excel / Access gurus?

I know we have a number of people on the site who know this stuff inside and out. Here's my situation.

I will be receiving a spreadsheet with about 2200 rows on it (including people's first and last names in individual columns). Let's call this Speadsheet A.

Spreadsheets B and C are massive files - B has about 54,000 rows and C has 118,000 rows. Both also have individual columns for first and last name.

I need to check each name on Spreadsheet A against Spreadsheets B and C to determine if any of the people on Spreadsheet A are on either of the others. Rather than searching each name by typing it in (twice) I am looking for a way to automate the process. 

Can anyone provide some ideas? I would prefer to insource this project instead of paying our IT company to do it. From my google searching it appears that this is very possible, but I have no idea where to start. Where are my nerds?