Hello Anu,
I think I worked out what your problem is. I think the only way to get what you want is to put a calculation of the growth into your original data table and include that in the pivot table as a field value.
Your only other option would be to do away with the year separator and label your quarters uniquely eg 09Qtr1, 09Qtr2 etc. Then the %Difference from previous will work as you require.
Regards
Harry