Hi Eli Schleifer,
Given that you have the rest of the DragDrop working (I could help you with this if you need), then you will most probably be doing something in the DragInfo handler with DragComplete status, lets say removing the item from the source object. Then probably you will be adding the dragged item(s) in the DropInfo handler - with DropComplete status.
What you could do is build an object that has delegates pointing to anonymous functions that do what you will normally do in the Drag/Drop info handlers. You can build this object in the Drag/Drop handlers and remember this object somewhere (also as a payload of the DragDrop). Then on drop info you show the user prompt and execute the actions only if they were confirmed. I suggested lambda (anonymous) functions because you could easily transform existing code into them, of course you could approach it differently.
Implementing this may not be trivial so please come back to us if you need an example or more clarification.
the Telerik team