I came up with this (below) which seems to work pretty well. FROMTO.EXE is my own creation to extract parts of a file between arg1 and arg2. It leaves stull that doesn't change when there are no new posts. Since the EGREP gets rid of ampersands (which really screw up processing the file with internal commands) you could probably do this without FROMTO. NOTAGS is in 4UTILS; EGREP and CMP are externals.
cdd %temp iff exist jpcheck.new then copy /q jpcheck.new jpcheck.old del /q jpcheck.new endiff type "http://jpsoft.com/forums" | notags | egrep -v "&|RSS|Sub-Forums" | fromto Latest Buy > jpcheck.new if %@exec[cmp jpcheck.new jpcheck.old > NUL] NE 0 (http://jpsoft.com/forums) else (echo No!) cdd-