Security :: Folder Level Forms Authentication

I am trying to implement forms authentication in my application. It has a folder named
User and an .aspx Page named Welcome.aspx. I am trying to restrict Access to this page by directly typing address in the browser. For this I have done following setting in web.config:

<location path="User">
<system.web>
<authentication
mode="Forms">
<forms
loginUrl="Login.aspx"
name=".ASPXFORMSAUTH"></forms>
</authentication>
<authorization>
<deny
users="?"/>
</authorization>
</system.web>
</location>

It works fine for the first time and redirects to Login page when I type the URL directly in browser. But when I press back button in browser and again try to redirect, this time it redirects to Welcome.aspx. How can I avoid such a situation (Don;t want to disable back button). Also If i try to Set Location Path="User", it gices error i.e. I am not able to set folder level security