This is designed for forensics, but there must be some use for it in removing stains, etc. Give it a try and report back.

http://home.planet.nl/~ber03728/4N6site/improc/decoplugin/main.htm

Windows only and some registration hoops to jump through, but it's a free and useful plug-in! I'm off to get it... Thanks for the heads-up!

I have a personal filter that is very similiar. Very handy for making those kinds of difficult selections. One use that kind of surprised me was making difficult fleshtone selections when rim-lighting was way over done.

Well, I still await my reply from them...

Bumped..
No longer FREE need to make a donation, Whatever you feel is appropriate (PayPal)