[TYPO3] Complex cache problem?

[Matthew Manderson]

I have a site using tt_news extensively and I have a $_SESSION being set and
displayed alongside the tt_news item in list view.

The problem is that the list view is being cached by default and so changes
to this $_SESSION value are not reflected in the page view.

Now the lazy answer is to disable caching for all the tt_news list view
pages.

However, this $_SESSION is only changed once or twice by each visitor per
session and so the remaining time they are browsing the list view will be
displayed fresh and not cached causing an unnecessary server overhead.

Setting the appropriate $_SESSION is done with a userfunc and so my question
is this...

How can the cache be cleared when a userfunc is called?

The clearCacheCmd looks close but how to call the underlying function from
the userfunc.

Thanks, 
Matthew