Hi Sunil,
This datasources is not standard, you can apply changes.
ECC side:
1. go to rso2 and check what is the source
2. you need check the structure, and add your field
3. i think you have a function module for extract, you need modify your program with your logic, if is a view, oly need check if you can add your field.
4. Save your changes and active
5. try load test in rsa3
BW side:
6 search your datasource, click right click and replicate
7 active your ds
8 try load your psa.
I hope helps. Luck.
Regards.