You can add div's and tables which have ID and runat="server" attributes set in the RadAjax UpdatedControls collection. Adding cells is not supported. You could also add RadPanelBar but adding single PageView or controls form PageViews is not supported scenario. You should add the whole RadMultiPage control into the RadAjax settings as described in the following help topic
I hope this helps.
the Telerik team
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