I am looking for a view where the users can only see the modified status but unable to edit it.i have a scenario reserving a seat for an event.if two agents reserves a same seat at the same time, we cannot tell under whose name it will show as in the...

I have a field where an agent selects a status and it will show last modifed by his name.But when another guy redo the same thing, it is changing to his name. How can i restrict modifcation of a field which is already done by one agent.