I'm trying to create a simple spreadsheet that contains tables for a Budget (By Category) and a list of Transactions (With each transaction belonging to a Category), and then a Pivot Table showing a summary of the Budget and Actual Spending by Category.
The basics are working fine, as shown below:
(The Blue table is Transactions, Green is Budget and the Pink table is the Pivot table)
To get the Pivot Table to work as shown above I had to create a Relationship, as shown below:

All good so far. The problem is that I now want to add another column to the Pivot table showing the remaining budget/overspend. i.e. The Budget for a category minus the amount spent for that category so far. (Or =Column2 - Column3)
Everything I've read online says I need to add a "Calculated Field" from under the "Fields, Items & Sets" menu, however this is Greyed Out for me:
I searched for why this would be greyed out and all I can find is that "Calculated Fields" cannot be added for OLAP sourced data, but my data is not OLAP sourced.
Help would be appreciated.
Thanks Ben



