I am pasting here my response to your support ticket with the same question for anyone else that may have a similar need.
There is no built-in way to do this.If you would like to see such a feature implemented in the control, I advise you post your idea together with a detailed description of how you would expect this to work and be exposed for configuration in our Feedback portal: http://feedback.telerik.com/project/108. This will let our clients review, comment and vote on the idea and if it gains enough traction in the community, our management will consider its implementation.
What I can suggest is that you obtain the data through your own code and store it in some object (e.g., a DataTable or some List<customObject>) that you can use as the chart's data source:http://demos.telerik.com/aspnet-ajax/htmlchart/examples/databinding/bindtolist/defaultcs.aspx.
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?
Telerik Feedback Portal
and vote to affect the priority of the items