Hi All thanks for your reply,
But the problem was in not in the BEX but the difference in the way the BW extarcts data from Virtual Cube and the way the Bex gets data from virtual cube. The Datasource responds to the filters in the BW rsa1 as a second priority because it first brings in the data and then applies filter. But the Bex does this the other way round. It filters the data and then brings it in. This was causing the issue.
The value that was being set in filter BEX was not present in the V. CUBE. But from RSA1 it was coming because the filters applied on it are deployed once data comes.
Once again I thank for your replies.
