pay per view does not prevent reaccessing the protected page

another bug in pay per view, even if I set up the cookie to 0, onc I have visited the content after paying, if I press back button on browser I can return to the confrim button page and access the content again!!!
This is not good because I want "one shot" access!!!
Not that the customer after seeing the content once can go back and see it again!!!
Please fix otherwise is useless!!!