Logout not working when hit of back button browser

HI every one...I have a problem which has be discussed many times already but i cant figure it out in my case ...The same problem of logout and avoid to use the back button to go to the secured page aldry logged out from it... IM Using VB to code
Here is my code for my Loggin page:
Session("Username") = Me.Login2.UserName
Response.Redirect("AdminPanel.aspx") and here in my secured page on the Load:
        Response.AddHeader("pragma", "no-cache")
        Response.AddHeader("cache-control", "private")
        Response.CacheControl = "no-cache"
        Response.Cache.SetExpires(DateTime.Now.AddMinutes(-1))
        Response.Cache.SetCach ...