DB_DataObject: M:N relations

Hi, DB_DataObject and DB_DataObject_FormBuilder can save me up to 30% of development time in one of my projects and I'd like to use them in this one as well as in earlier projects. However, this one needs a <select> input in the form with the possibility to select multiple items at the same time. In relational databases we store this using 1:N - N:1 relations with an additional table between them. (e.g. clients - clients_services - services). My problem is that I don't know if I implement such a feature should it be really in DB_DataObject or another class should be created using multiple DataObject-based components. I think the best would be to implement this in DB_DataObject so it could store the whole "client" form in one turn ($clienttable->insert()), and even DB_DataObject_FormBuilder can use it to generate the corresponding html element.. If anyone could help me on how to do this, I'd be happy to implement it in both DB_DataObject and DB_DataObject_FormBuilder and post it to the list. Any ideas are welcome. Norbert Mocsnik