Gridview on refresh

[Guest]

I have a gridview that allows users to edit records. In reality, I've
changed the SQL so the edit is actually doing an insert to a date driven
table. Works great. Unfortunately it works too good. The user performs the
update and the gridview posts back. However, If the user hits their browser
refresh button here, the "update" (actually an insert) happens again and now
I have duplicate rows in my db! How can I prevent this from happening
(previous gridview action on a browser refresh) without loading a different
page?

Thanks! -Matt