ASP.net C# - How do I default the User Name to the Login control when users select Remember Me?

I have a strange requrement twist on the Login RememberMe function.  When a user selects RememberMe on the Login Control, I have to default in the User Name and check the RememberMe box.  Upon Login, if they de-select the checkbox, then stop defaulting in the User Name and uncheck the RememberMe box.  

The idea is that the user will always be required to type in thier password in order to log in.  I've tried several variations of using either the membership or cookies, but then have an issue with how to log out or de-authenticate the user while keeping the cookies.  

If I do a FormsAuthentication.SignOut(); I lose the authentication ticket, so I was trying to do a HttpContext.Current.Session.Abandon(); and then just look for the cookie.

I can set the text box properties and remember me properties of the Login control using this code:
TextBox un = (TextBox)Login1.FindControl("UserName");
                un.Text = rmCookie["RememberMe"];
                Login1.RememberMeSet = true;
But if you try to put this in the page OnLoad event you get stuck and can't login - I believe that's because it's causing a changed event on the textbox.

None of the things I've tried have worked.  i'm thinking that surely someone out there has done something like this and it's fairly simple.

Any ideas on how to make something like this work?  

I'm doing aspx.cs (code behind) with an asp.net 2.0 Login control.