We have several stock items that continuously change which are input/managed in a 'Service' form. I want to use a multi select list on another form 'Subs' that calls these items for selection. We need as we want to be able to select combinations of the current stock from the list. 

Either that or have a 'add new' lookup button that will great a new lookup line.

Is there a way to do this or is this a limitation of creator?