Prevent users using the back button.

[eluser]richzilla[/eluser]
How can i prevent my users from using the back button on their browser to return to a secured area after theyve been logged out? at present i have a simple logout procedure:

Code:

function logout() {
            $this->session->sess_destroy();
            $this->load->view('site_view');
        }

and the login check for my secure pages is:

Code:

function secure() {
            if ($this->session->userdata('loggedIn') == TRUE) {
                $this->load->view('secure_page');
            }
            else {
                $this->session->set_flashdata('status','You must be logged in to view this page.');
                redirect('site');
            }

yet after my users have logged out of the page, they can still click the back button and return to the visited page?

any help would be appreciated.

Thanks.