Help with multi select

Just re-iterating this as did not get a response.

I have a multi select box in which a number of filters are applied to so that when the final selection is displayed the use has only a few choices.

Of the 200 parts, by selecting a site, and then a fault type the list is reduced to 6-10 selections. This work fine while there is nothing selected, but once the incident is edited, the selection is lost, and I want to re-apply the selection (which is often more then one part of equipment) so that it reflects what was originally checked.

As an alternative solution, is there a way, when a picklist is loaded, that only the currently selected picks are shown. Not the entire list? If my crew want to change it, they select the site, then fault type to reduce the list down again, and reselect what they need....