Email Validation Issue

Hello,

I am needing help with email subscription validation. I am needing my visitors to only access a certain page by subscribing to my list. However, I am still needing people that are already subscribed to be able to access the other page through this page(form), unless a better alternative is possible. Is it possible to have a validation say ‘Thank you, you are already subscribed’ and then redirect to the next page?

https://www.ads-software.com/plugins/contact-form-7-mailchimp-extension/