I appreciate the links. The one that b.e.wilson recommended, http://www.largeformatphotography.info/dofknob, is the one that I was thinking of.
Some time ago I downloaded VadeMecum ( http://www.bobwheeler.com/photo/Software/software.html ) for my PDA. I haven't used the software, though, and I don't think that I will. This isn't to say that these programs aren't useful; when I'm photographing I, personally, want to photograph, not play around with another computer (I use a computer way too much, already). I might use one of these programs for a limited time to become further acclimated to the DOF of LF.