Converting Indents to Outline

I have a set of macros that creates a directory tree listing on an Excel
worksheet for any folder that I select. It drills down to the lowest
sub-folders and lists the local and global disk space taken up by each
folder, along with some other statistical info. Column B holds the name of
the folder, and these names are indented to reflect the level of the folder -
a poor man's Explorer.

What I am trying to do now is extend this by creating an outline by grouping
all the folders with the same level of indenture at the same outline level.
At the highest outline level, only the top-most folder will show. Below
that, the grouping must be done recursively. Since you can have 15 indenture
levels, but only 8 outline levels, the lower level folders would all be in
group 8.

Has anyone seen a method or macro for doing this? I can do it, but it will
take time and if there's a good starting solution out there I would love to
see it.

Thanks in advance,

Eric