How to change the database connection properties of Crystal report ( web service ) at run-time?

Question

Hi ,

              I have published a crystal report as web service and consuming the report in web page and windows form with the help of crystal report viewer. I have a database with same named (also same structured )tables in SQL server and Oracle. The report should use either of the database servers (SQL / Oracle) to get the data based on the key (in appSettings section) specified in "web.config" file.

1. How can I change the database connection properties  of the crystal report at run-time such that the report  should use one of the database servers?(Note: Report is published as web service)

Thanks in advance,
Satheesh