C#-Messenger Feature - Update system

I am not sure how to explain what I am needing done but I can give some examples. One example is if you ever used Yahoo Messenger then you know in the help menu there is an option called "Check for Updates" and then of course it will do this and update the program. This is what I am wanting done.. My app will be downloadable from my website and then either the user can do it or have it do it automatically it will check for updates and upon updating it would close and update then restart the app. I need an sample project of this. with documentation of what I do to setup this to work with mine. The sample app would have to have some sort of progress bar showing the update and such. I would being using the sample and modifying it to work with mine so I need this sample to be good and firm. Questions ? please ask me