As far as I understand from your explanations, by disabling the sliding zone you mean that you want to disable the drag and drop functionality of the RadTreeView. If this is correct, in the DisableDashboard function ayou should obtain a reference to the treeview by using the method $find and then call the set_enableDragAndDrop
methods with argument false. Both the method are listed in teh client API reference of the tree view control which is availabkle below:
In case this is not what you want, please provide more detailed information on your exact goal.
the Telerik team