Software developer required

I need someone to write a simple application that can:

1) extract e-mail addresses from large plain text file where the e-mail addresses could be in the middle of long lines of text
2) compare these extracted addresses to those in an excel spreadsheet or CSV file
3) mark those that it finds in an adjacent column.

Ideally the application would have a security element so that people had to apply for a key to install it on their local drive.

This will be to help my clients remove rubbish e-mail addresses from their mailing lists.

Many thanks

Chris