Aruna,
Take a look at this thread. As i explain in that, the Credit Limit is contained within a seperate Business Object.
Check with SAP whether that exists in another data source, or if it's within a data source planned for an upcoming release (in either case you'll need to join that in).
Alternately, they may direct you to the Cloud Service Center, as it's something that could be created within a custom data source for that particular object within the SDK, or even to a development partner such as my company.