Unfortunately, we do not have support for this feature built-in the listbox control. However you can always put some buttons next to the listbox and implement it on your own. You can use in the implementation the Items collection of the control and the methods of the collection such as Add, AddRange, Remove, Insert, Clear. For example pressing the "Up" button will remove the selected item from the collection and then you can insert it one index before the selected index. The "Down" button will remove the selected item and insert it one index after the selected Index.
Feel free to write me back if you need more information.
the Telerik team