I need my membership system to auto-approve registrations based on fields matching

General information for the website: A members only area for existing members
Kind of development: Customisation of existing website
Num. of web pages/modules: 1
Description of every page/module: We use the wp-members plugin to restrict some pages to existing members. We have over 2000 members who are already members of the organisation but have not used the website yet.

When a user registers they enter their name, membership number and email address.
The wp-members plugin then sends an email message to the admin. We then manually check the details (Membership number and name) to make sure they are in-fact a legitimate member and not a non-member or a robot. We do this by looking on a spreadsheet and then 'activating' the new member on wordpress if they are valid.
Description of requirements/features: We would like the system to automatically approve new members if their membership number & surname match a record on an uploaded CSV file. This would save a lot of time so that we ONLY have to manually activate users if the membership number and surname do not match.
When a user registers and their credentials match our existing list of names/membership numbers, they will be automatically approved, an email will be delivered to them to say that they are approved and they can use the members area almost instantly.
Note: An 'You have been approved' email is already automatically sent, but only when we have manually 'approved' a new user.
I expect that we would upload an updated CSV file with surnames and membership numbers every week or so to update the database of our members. Perhaps by FTP?

Final Note: Perhaps there is a plugin that will already do this? I can't find one. But i'll be happy to pay just to find out what plugin to use.

Thanks
Extra services needed: Customization, 3rd party integration
Specific technologies required: wp-members, wordpress, ftp, csv
Extra notes: