Hi Palaiappan,
You cannot, unfortunately, sort on formula fields that refer to aggregate functions.
You have a few workarounds:
1) Calculate the percentage in the BEx query
2) Use a Subreport. This BEx query would run twice with this approach and might slow down the report too.
3) Use a Crosstab.
- Add the 'Account' field as the 'Row'
- Add the '$Change' field as the First Summary Field and set its Summary function to 'Sum'
- Add the '$Change' field again and this time select 'Change Summary' > Check 'Show as percentage of'
- You should now be also able to sort the crosstab 'Row' based on the Percentage summary.
-Abhilash