Thank you for this question.
This feature was implemented in an earlier release of RadGridView. After a major refactoring of grid's data layer, we removed some rarely used features. We will consider adding this feature in Q2 2008 SP1.
As to the source code, if you have purchased a Subscription license, you will receive it as part of the package.
I hope this helps. Do not hesitate to write me if you have other questions.
the Telerik team
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