If I can get that working I would then like to create a portal in the exhibit table layout that will list all the pieces of artwork that have been entered into that exhibit.
This is where I would start. I would have the portal in the exhibit layout, where I can enter the pieces of art I want to add to that exhibit. That should be a related table called ArtworkExhibited. It would be the same as a line items table in an invoicing solutions. One exhibit will have many pieces of art. Actually when I add a piece of art to an exhibit, I would do it thru a picker window, then after you select the piece or pieces of art, they will populate on the exhibit's portal.
The same applies to the Artwork table. Except that portal should only show which exhibits that particular piece of art was exhibited-also a one to many relationship. If I wanted to add that artwork to an exhibit, I would have a picker window of exhibits, select proper exhibit. This should do 2 things, capture the id of the exhibit, capture the id of the artwork, go to ArtworkExhibited layout, create a new record and populate both the foreign keys in that table. That will in turn place this 'lineitem' in the portal on the Exhibit Table. Which will in turn also populate the portal on the Artwork layout