Handling sub-folders Custom Site Map?

Question

  I am attempting to make a Custom site map provider for the first time, but I am stuck on the sub folders. When I try to add my files and folders I am not sure how to build the path for the Directory Info as it drops down a level in the folders.
Example:
It starts out as ~Content  for the Root
~Content/folder   for the folder
~Content/folder/file for the file
but when I get to a sub folder(s) I am not sure how to append the path to something like this:
~Content/folder/folder/folder/file    as it loops through the sub-folders.

I appreciate any help as I am in over my head.