Compare data in two pivot tables

Hi,

I have daily data for 4 years which I have summarized in two identical pivot tables.

I would like to be able to easily compare the two tables (in another table?) so I can get: for example the percentage difference between January in 2014 and 2016 by setting the first table to 2014 and the second table to 2016.

I need the pivot tables to remain customizable i.e. can easily group and ungroup data by columns (month, quarter etc) and rows (there are two levels of data in the rows).

Ideally the camparison table would also be custonizable like a pivot table.

I think Getpivotdata is an option except you can't copy down the formulas (?) so I would have to populate each cell of a comparison table individually (the tables are about 50 by 365 when fully expanded). Also then you have the REF error problem when you collapse the pivot tabels. Surely there is a smarter way of doing this?

Any ideas?

Many thanks in advance.

T