Get treeview selected path as a string

Hi All,
I'm dynamically generating a tree view on the folder structure on client machine:
C:
  -- Folder 1
  -- Folder 2
D:
  -- Folder 1
    --- Folder 11
    --- Folder 12
  -- Folder 2
etc...
When the user expands and select - say folder 12, I want to get the path as D:/Folder1/Folder12 in to a string
then when the user changes the selection to D:/Folder1 i want to get that path in the string.
What is the easiest way to do this?
Thanks in advance
...