[Typo3] dynamic parameter for tt_news

[Daniel]

hi to all,

I would display on a site always the lastest created category (of the
extension tt_news).

So I execute a SQL query in my TS setup and I get always the right
result: the uid of the last created category.

But I don't know how I can assign this result to the configuration of
the plugin.

I've tried with:
plugin.tt_news.categorySelection <= temp.test
and with
plugin.tt_news.categorySelection < temp.test

but with any success.
Can someone give me a hint how to do this?

bye,
daniel