As the scenario you need to achieve is rather complex I would suggest you to open a regular support ticket and send us sample runnable application which shows the exact functionality you need to achieve. Thus we will be able to debug it locally and verify what the exact reason for the mentioned error is and provide proper solution.
All the best,
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items