Excel 2007 : Excel Pivot Table - calculated rows???

I'm trying to figure out how to have two calculated summary rows in a pivot table. (The default is a sum summary total.)

My data table has the following columns:

- Group
- Amt Spend
- Category
- Year (values of 2008 & 2009 only)

My pivot table has the Group & Year as the row labels and the category as the column labels with the Amt Spend summed as the data.

As mentioned, I don't want to show the subtotals (I figured out how remove those); however, I do want to show two summary lines for each group showing:

1. the amt spend difference between 2008 & 2009
& 2. the % difference of spending for 2008 & 2009.

If it's not possible to have 2 summary lines, I would rather have the amt difference.

Any help?

FYI - I do see that I can select (Summarize Data By > More Options > Show Values As > Difference From); however, that changes all data values, not just the subtotal line.

Thanks.