How do I refresh a page ONLY ONCE using JavaScript especially when a user clicks the 'Back' button of his browser to go back to the previous page?

For e.g. assume that a user is in Page1.html. He clicks a link on this page which takes him to Page2.html. Next the user clicks the 'Back' button of his browser taking him back to Page1.html. How do I refresh Page1.html ONLY ONCE when the user comes back to Page1.html?