Plugin to prevent page edit

Hi folks, I created and run a good few wordpress sites for the company that I work for here in Ireland. I have been looking for a plugin that would allow me to lock a page, i.e. once I the administrator have it created then no one can edit it. I was wondering is this currently in the realm of possibility without butchering or going near the wordpress core which I am not willing to do as I must maintain the integrity of the sites core in order to allow seamless updating with current wordpress versions. Any info is appreciated.
Thanks.