How do I automatically add contact information from Mac Mail E-mails to a specific group in Contacts?

I'd like to add a Mac Mail rule that runs a script to add the contact information of all incoming E-mails to the "jen@[domain]" account to an "Event" group in Contacts. I only need to add the first name, last name, and E-mail address for each. And obviously, I don't want to add duplicates.

I've seen a few AppleScripts online that say they'll do something like this, but they're all from like 2009, 2011, etc. Some clearly say they won't work beyond 10.8. And I need something that will work on Mavericks and Yosemite.

I'm fairly good with logic and code, but don't know AppleScript at all and haven't been able to write what I need myself ... I need some help!