C# - How To Do Multi User Editing

I have a system where I would like to show a warning to a user if there try and edit a record that is currently been edited. If this is the case the user will not be able to save the record but only view it.I have an idea of using some kind of class to monitor the activity of records been edited etc but this seams a little over kill. My other concern is that what if the browser crashes or there shut their computer down on how this will effect the state of the page.

Another thought was to use last updated time stamp but this also looks a no go because the way records are been updated? how I could implement something like this. No code is necessary.based on the comments I have added these additional details.database is SQL server 2008 asp.net 3.5 one record could be many parts of the database for instance, the booking table session table and a row in the interrupter table.the user will look at a list of sessions that need booking select a booking and fill out a booking form to make the booking. Want to stop is someone else trying to do the same booking at the same time or while someone else is doing the booking.