I am not sure that I understand your requirenments 100%…
Let us say you have 15 different values that you want to place within three different groups:
A: (1,2,3,4,5) B: (6,7,8,9,10) C: (11,12,13,14,15)
This can be solved with four static lookups, one NSQL lookup and two attributes on e.g. project object. First Attribute will point at static lookup (A,B,C) and second attribute will use NSQL lookup to display list of values that is dependent on what is chosen in (A,B,C) lookup.
Is this the solution you are looking for?
Br
Davor