Does anyone out there know how can get a tree-view to allow mutliple selections within a level (for the purpose of dragging and dropping the selected items to a new "parent")?

For example, if I have the following structure:
A
-1
-2
-3
B
-4
-5
-6

and I want to multi-select and drag items 4 and 5 to level A, how would I do this? (I already have single-selection drag and drop working).