Here are the steps to display the difference between FY 2008 and FY 2009 in the Grand Total column of your pivot table:

1. Click on the Grand Total cell in your pivot table.
2. Click on the drop-down arrow next to "Sum of Grand Total" and select "Value Field Settings".
3. In the "Value Field Settings" dialog box, select "Difference From" in the "Show Values As" section.
4. In the "Base Field" drop-down list, select "FY 2008".
5. In the "Base Item" drop-down list, select "(previous)".
6. In the "Compare to" drop-down list, select "FY 2009".
7. Click "OK" to close the dialog box.

Your pivot table should now display the difference between FY 2008 and FY 2009 in the Grand Total column. If you want to change the format of the values, you can right-click on the Grand Total cell, select "Number Format", and choose the desired format.