#3. "RE: Zone System Display" In response to Reply # 0
This is not quite what you are asking either, but it might help. Power Retouche Black & White Studio (a plugin for PS) contains a variation on the "zone" system by allowing three independent "zones" (or selection masks) to be created for your B&W image by using an eyedropper to select the "zone". They offer a demo that actually contains a lot of image editing capability but I have never really used it as my head is spinning with trying to learn other software. Hope this helps.