how to solve reloading previous page after unset_userdata() or sess_destroy() used in logout function????

[eluser]mythilisubramanyam[/eluser]
i have a function called logout in my Controller for destroying session and redirecting to login page,

Code:

function logout()
{
   $this->session->unset_userdata('empid');
   $this->session->sess_destroy();
   if(!$this->session->userdata('empid'))
   {
       $this->load->view('login');
    }

}

in this function empid value is cleared and login page is loaded.
if i click back in the browser the previous page is reloaded.

but the previous page shouldn't be reloaded,
even i checked for sesion empid value for the previous page to load,
even then its not working ....

can any one give a solution for this,