prevent multiple login in asp.net without database concepts

Question

I am using Form Authentication in my application using Asp.net 4.0.


1. Browse http://localhost/Login.aspx in IE.

2. Fill username and password.

3. OnClick on Login button ,then redirect to home.aspx.

4. Open new tab and browse same URL http://localhost/Login.aspx without closing already logged in tab.

5. Here i want to validate the user. If the user already logged in that should redirect to home.aspx.

6. If the user not yet loggedin, that redirect to Login.aspx


Page_Load()
{
// here i want to validate URL http://localhost/Login.aspx wheather it is loggedin or not
// if yes
// Response.redirect("Home.aspx");
// else
// Response.redirect("Login.aspx");
}

btnLogin_Click()
{
username and password verified here.

FormsAuthentication.SetAuthCookie(txtUsername.text, false);
FormsAuthenticationTicket ticket1 genearated here
Encrypt the cookie using the machine key for secure transport
Set the cookie's expiration time to the tickets expiration time

if true
Response.redirect("Home.aspx");
else
Response.redirect("Login.aspx");

}

Thanks in advance.....