Additem

I have this code and use it to move info from a datagrid, but when i display it in a list component it dosent ad to the last added item but it replaces them all, how can i make it add to the list in the dataset? and how can I add multipled selected items in the datagrid???
is there a waY?


btn_valja.onRelease = function(){
    DS_lista.addItem({vaxt:theList.selectedItem.SvensktNamn});
}