I can't open your workbook because it is using a live connection.
However, by reading your description, it seems like you can break apart the location dimension like so:
Calc 1: IF [Location] = 'Screeening' then [Weight] END
Calc 2: IF [Location] = 'Drying' then [Weight] END
Then take difference of the 2 calcs.
Hope this helps!
Sorry about the workbook! I'll try your calculation!