Simple page redirect

Site URL: https://www.ariento.com/new-user-request/new-user-request

Hi - I am trying to simply redirect to an upsell page after the product is added to cart and the custom form is filled out. I don't need any checks on product inventory or anything else as it will always need to go to the next upsell page once the custom form is filled out. I've found numerous scripts that will do it after add to cart button is clicked, however that doesn't work when there is a custom form. Any help would be much appreciated and I am willing to pay for a quick script deveolpment if that is what is needed. Thanks!