renaming folders

for renaming folder i use the following action:
action > format value > field: _DIRECTORY

works perfect, of course.
just one little problem with characters which are not supported in folder and file names:
/ \ < > : * | ? "

mp3tag treats them as if there was no character at all, it just omits them.
is there a way to get an underscore _ instead of the special characters in the folder names?

This what I use for filenames, it replaces special characters with an underscore:

$validate(%artist% - %track% - %title%,_)

You should be able to modify it for folders.

Thanks, works perfectly.
I had to place
in front of the existing renaming actions and
after it. Easy. Thanks.

That raises another question:

Is there any place in the forum or help page where I can look up all existing commands like this? Never heard of $vailidate(s,_) before. Where can I look up those tricks? They appear in the forum all the time, but is there no place where all those little action commands are collected?

ok, found it myself:

first search, then ask.
i know...