Caching forever until the file has been edited by the backend

[eluser]Unknown[/eluser]
I have created a web site using code ignitor. It does not require any user interaction on the front-end however there is a backend where my client will login to add and edit data. I want to always serve a cached file to the user agents and refresh the cache every time that the client edits from the back end. How do I set caching to not refresh the cache ever with

Code:

$this->output->cache(n);

and where should I start to implement the back-end to allow the cache to refresh. I would assume I could use hooks to intercept the back-end pages every time an edit occurs. I will be using a database (mysql) to save the clients data.