You can not add additional columns for the DataTable. You can place the Chart inside the Grid's Footer. Then You can export the Grid as a single JPG.
These links can help you:
Grid and Chart in TemplateColumn
Totals in Grid Footers
I hope this helps.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed