JS Exit-PopUp for wordpress site

Hello, I need an unblockable javascript alert exit pop-up for my Wordpress site (developed and installed): - it should show up only on pages with order forms (currently 6 pages) - should be displayed only once on each page for one session - should show up only when a visitor clicks X button to close the browser - shouldn't show up when a customer is redirected from the order form to a payment gateway (this is the main problem with ready exit pop-up plugins - even if external urls to block the pop-up are added, the pop-up still shows up when a customer proceeds to a payment gateway) - an additional Mailchimp event tracking function should be added to "Leave page" button (when a visitor clicks "Leave page" this event is recorded in Mailchimp and a follow up email is sent to a customer) Thank you in advance for bidding. Kind regards, Margarita