Editors Note: TVR found an undocumented feature:
Functions Documentation
View Function Edit Function
Name scrSetListFilter
Syntax (scrSetListFilter screen criteria)
Argument List screen: The screen you want to filter the items on.
criteria: The criteria string you want to filter the item list with.
Returns condition: True is successful.
Category screen
Description Sets the list filter from the given screen. Will only display the items that fit the criteria.
(scrSetListFilter gScreen "*U")

The current screen lists all the non equipped items.
Comment Very helpful in filtering item selection screens like loot screens.