Controlling Cache on Views

[eluser]FlashUK[/eluser]
I have a question about caching views from controllers. I have already searched the forums + google and haven't found a suitable answer yet.

In Smarty you could omit sections from being cached so that they could dynamically generate (link to documentation).
This was often used for things like display a users Username on a page when they are logged in, displaying a current timestamp, etc.

I want to know how you can do this with CodeIgniter's cache. I know you can set the timeout on the cache "$this->output->cache(n);" but how do I tell it not to cache certain sections in my views?

Thanks