[TYPO3] dont't cache output of ext

[Felix Natter]

hi,

I've coded a simple extension that inserts the right stylesheet
based on a session variable (using
$GLOBALS['TSFE']->additionalHeaderData[$this->baseId]='<link...').

In my template I call this ext with:
page.101 < plugin.tx_fontsizecss_pi1

The problem is that the output is cached: my ext is only called
once after I clear the frontend-cache.
How can I disable the caching?

thanks,

-- 
Felix Natter