Exclude folder "myfolder" only in root, not "something/myfolder" etc.

Hi,
is there a way to exclude only /myfolder not something/myfolder or something/something/myfolder etc. ?

You write: "you can use twentyten, theme/twentyten or public/wp-content/theme/twentyten"
But when "twentyten" folder will be in root, how to define to only exclude this folder in root, not all folders with this name in entire folder tree?

Thanks,
Jiri