FormBuilder : crosslinks question

Hi everybody, Here is my problem : 1/ I have a m:n relationship between DOCUMENTS, COUNTRY. So I have 3 tables DOCUMENTS, JOIN, COUNTRY. 2/ In COUNTRY, I have a flag saying if a country is in the EU or not. 3/ I have set up FormBuilder to display a multi-select filled in with the countries in the DOCUMENTS form. Ok, simple. 4/ I can filter the COUNTRIES with the prepareLinkedDataObject function, so that only COUNTRIES from the EU are displayed. 5/ For some reasons, what I want to do is to display 2 multi-select : - one with the COUNTRIES inside EU - one with the COUNTRIES outside EU And I really cannot figure out how to do that. Any idea? Thanks a lot. Thomas Balthazar.