I want to make sure that a user isn't editing the same form data in two different browser tabs or windows (of the same web browser instance). It's to stop the user from stupidly overwriting their own data as they continue through a very long form process. On the server ongoing data input through the screens is collected into the Session.

Assume for any browser, all tabs and windows run in the same instance of it (i.e. not each in a separate process). Obviously the browser tabs and windows share the same cookies in this scenario so cookie modification seems out of the question for viable solutions. This is also the reason they shared the same session.

Considering that the form is already created and this is one of the final touches, how can I use ASP.NET, hopefully easily, to oversee this "feature"?