[TYPO3-ttnews] mapping field value with a category

[Bernhard Karimi]

Hi list,

when a text field (i.e. author) has a certain value, then a
corresponding category should be marked as well.
Where and how can I accomplish that best?
In the newsRepository? In the TCEForms->getSingleField_preProcess?

[Typo3 6.1.5 and news 3.4.0]

Thanks in advance!

Bernhard