Dynamic multilevel Value list

Hi there, I am new to this world and I spend the whole day yesterday reading up, but could not find something that would deal with my specific problem, if I have overlooked something, please do point me to that thread.

Here is my problem.

I run an Art Gallery and want to set up a contact database. In this contact database I want to store all information about everybody possible. So the first file is contact details. Then I have separate files to specify what kind of contact I have with the individuals. f.e. Artists, and Art buyers. In the Artist file I want to store stock information. Paintings the Artists brought in, if it is in exhibition or if it has been sold, or taken away by the artist. These are usually unique, but he might have brought a print. (there is a multiple copy of one artefact) This also records the price for the art work and the commision to us.

Now my problem is

In the Art buyer file, I want to have a Value list, that provides the artists, whose work I currently have in exhibition, than a shrinking valuelist, for all the work that is currently available and a transferal of the additional price information to the artbuyer entry. And then in a separate field on the Artist entry the amount of outstanding payment to him.

Uff. I hope this is not to difficult.

Thanks for your ideas in advance