Example of how to handle formdatasource multiselection through args:

public static void main(Args _args)
{
    Common                  record = _args.record();
    FormDataSource          fds;
    MultiSelectionHelper    multiSelectionHelper;

    if(!record || !record.dataSource())
        throw error(Error::wrongUseOfFunction(funcName()));

    fds = record.dataSource();

    multiSelectionHelper = MultiSelectionHelper::construct();
    multiSelectionHelper.parmDatasource(fds);

    record = multiSelectionHelper.getFirst();
    while (record)
    {
        // function here
        record = multiSelectionHelper.getNext();
    }
}