[TYPO3] test whether a certain data structure is on a page

[siska]

How can I test with Typo Script whether there is a FCE of a certain data 
structure on a page or not?

Example:
On some of our pages, but not on all of them, we have relation to other 
pages. The relations are stored in a Flexible Content Element. They are 
shown in the Front End in a box and this box i empty when there are no 
relations. I want to hide this box when there are no relations.
How can I do that?

-- 
regards
Barbara