Thank you for your question.
You can find the answer to your question in this help article
, under the section 'Populating cells'.
I hope you find it useful. Feel free to ask if you have any additional questions.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.