"Expandable listing" in ListView or ListBox

I have an index-file containing the contents of a
directory/file-structure, like this:

//Index of drive c:\ [master]
c:\autoexec.bat
c:\config.sys
c:\dos
c:\dos\filename.exe
c:\dos\temp
c:\dos\temp\file.tmp

When listing this in a ListBox, all lines are displayed (like above)

What I'd like to do, is to be able to show only the top directory (w/
files):

c:\autoexec.bat
c:\config.sys
c:\dos

And then be able to doubleclick on c:\dos, to display:
..
c:\dos\filename.exe
c:\dos\temp
c:\dos\temp\file.tmp

Where the ".." should bring me back to the previous level (i.e.
ordinary file manager stuff).

Since I'm trying to learn Delphi, any help will be greately
appreciated.

Thanks in advance,
Jarle Aasland
NORWAY

(Please respond both to group and directly to jaas...@online.no)