Subtracting one value list from another

[Jarvis]

I have a value list called PLAYERS that is populated with the following custom values:

Architect

Contractor

Cabinetmaker

Electrician

Painter

I have two fields:

People who should be notified

People who have been notified

These two fields are displayed as checkbox fields using the value list PLAYERS

I would like to have a third field that just displays a checkbox list of the Players who NEED to be notified.

Any way to do this?

[comment]

See:

http://fmforums.com/forum/topic/52332-speedy-value-filtering-may-07/page__p__245860