Change Add to Cart Redirect on Woocommerce After Form Submission

I have a Woocommerce site which has a redirect to a Contact 7 Form when an item is added to the cart. The form is intended to collect customer information to cover the whole order. I only need the form to be submitted once, rather than each time something gets added to the cart.

Can anyone suggest some conditional code snippet that I can add to the redirect that would check for submission and not call the redirect if the form was submitted already?

Thanks!