how to force an email capture before going to pages

I am building a site with this requirement: When the user attempts to navigate to certain pages, they will be forced to fill out a small form (enter they email address) before they can get to the desired page. On a standalone site I’d do this by looking for a cookie on each protected page, and if not there, redirecting to an email capture page, along with a url parameter indicating the page to go to after they enter their email.

Now- how to do this in wordpress?