Using ASP.NET to Prompt a User to Save When Leaving a Page

searching for my problem lead me to Using ASP.NET to Prompt a User to Save When Leaving a Page by scott mitchell.
but i need a simpler way. i wnat to prevent user from leaving page when my FormView is in Update or Insert mode.

Prompting a User to Save When Leaving a Page

about a day searching for it, just didn't know must return nothing!

Prompting a User to Save When Leaving a Page
http://www.4guysfromrolla.com/webtech/100604-1.shtml