try this
Response.Cache.SetCacheability(HttpCacheability.Se rverAndNoCache);

or any flavor of the httpcacheability enum

"Karl" <nospam@nospam.com> wrote in message
news:e#$Xg6BPDHA.1072@TK2MSFTNGP10.phx.gbl...
> Hello:
>
> I am new to ASP.NET. How do I make a page expire to prevent users from
> updating records that are already updated. ex.Clicking Back on the browser
> and then resubmitting the page? Thank you in advance.
>
>