One way to do this would be to create a very manual calculation similar to the following:
if attr([Sub-Category])='Bookcases' then 14000 elseif
attr([Sub-Category])='Tables' then 3500
Then, place the calculation on the level of detail shelf. When you add the reference line, choose the calculation for the value and be sure to select Per Cell for the scope.
Hope this helps!
Worked like a charm Tracy. Thank you!