[TYPO3-english] Get flexform or TS value in a flexform

[Viktor Livakivskyi]

Hi, List.

We're developing an extension, that shows company subsidiaries. Subsidiaries 
are just records in tx_subsidiaries. FE plugin just outputs a list of them 
inside an accordeon, but BE user must be able to select, which subsidiary he 
wants to show as default opened in an accordeon - the best case is 'select' 
type, which shows all the subsidiaries.

But the problem is, that there might be more, than one storage folder, that 
holds subsidiaries, so every plugin instance may have it's own storage 
folder selection field set in a FlexForm, and list, shown in 'select', must 
depend on selected storage folder.

The question is: how can I get field value (let's call it storageId) in 
<foreign_table_where>AND pid=[storageId]</foreign_table_where> ?