Adding % Difference to Previous Period (Year / Month / Qtr) into Pivot Table

[#1]

Hi.

I have set up a pivot table that has Year, Quarter and Month as Rows and measures:

Number of Parties   - Sum([BubAdm_Number of Parties])

Party Children         - Sum(BubAdm_PartyPeople)

Average Party Price     - Sum([Party Income from Days Parties])/Sum([BubAdm_Number of Parties])

Average Spend per child      -  Sum([Party Income from Days Parties])/Sum(BubAdm_PartyPeople)

I want to add a column next to each existing column that shows the difference and % difference to previous year for each figure.

I've no idea where to start on this sorry.

[#2]

Hi all, I'm assuming it's not possible to do this then?