Overriding Fetch() method

[teertha13]

I have 5 five columns in a data row. They are GroupName, Date, AMT1 ,AMT2,AMT3.
My report is build by metadata i.e controls are created on run-time. For customization I need to override methods.
Data will be like this
GroupName Date Amt1 Amt2 Amt3
ABC 01-01-2007 100 100 100
02-03-2007 100 2002 300
05-06-2007 200 300 400
QWE 01-01-2007 100 100 100
02-03-2007 100 2002 300
05-06-2007 200 300 400
If groupname is different I need to do average for the columns AMT1 ,AMT2,AMT3.
How to override Fetch() for this.The report output should be like this.

GroupName Date Amt1 Amt2 Amt3
ABC 01-01-2007 100 100 500
02-03-2007 100 200 300
05-06-2007 100 300 400
Average: 100 200 400
QWE 01-01-2007 300 100 200
02-03-2007 100 200 300
05-06-2007 200 300 400
Average: 200 200 300

I want to add the datarow which calculates the average.
Please help me on this. this is very urgent.

Thanks in advance