help with rule request

Help...anyone...

I want to craft a .procmailrc rule like:
get the Subject line and parse it into a FILENAME to be used to
log emails each containing a single line of data
Write that single line of data to $FILENAME

SHELL=/usr/bin/ksh
:0 c
* ^Subject: XXXXXX
* ^From:(_dot_)*something(_at_)domain(_dot_)com(_dot_)*
# other filters here?
  |export FILENAME=`formail -xSubject: |sed -e 's/ //g'`
  :0 A
  # formail -I "" gets just the body, the sed stuff strips blank lines:
  |formail -I "" | sed -e '/^$/ d' >> /path/log/${FILENAME}

where FILENAME would be determined from Subject field via:
  FILENAME=`formail -xSubject: |sed -e 's/ //g'`
  (yeah...some red flags here security-wise, but I can deal with that later...
   hopefully with better sed expressions)
and the body of the message would be appended to $FILENAME via:
  formail -I "" | sed -e '/^$/ d' >> /path/log/${FILENAME}

Problem is that above doesn't work...seems the second filter doesn't
get the value of $FILENAME passed?

FYI...if I use:
:0 c
* ^Subject: XXXXXX
* ^From:(_dot_)*something(_at_)domain(_dot_)com(_dot_)*
# other filters here?
  | (export FILENAME=`formail -xSubject: |sed -e 's/ //g'` ; \
     echo "${FILENAME}" > /path/log/out1)
  :0 A
  # formail -I "" gets just the body, the sed stuff strips blank lines:
  |(echo "${FILENAME}" > /path/log/out2 ; \
    formail -I "" | sed -e '/^$/ d' >> /path/log/foo)

I end up with:
-rw-------   1 dwm      dwm           24 Oct 28 16:55 foo  <- data - good!
-rw-------   1 dwm      dwm            7 Oct 28 16:55 out1 <- XXXXXX - good!
-rw-------   1 dwm      dwm            1 Oct 28 16:55 out2 <-blank - not good

anyone with clues to offer??
Thanks
Doug Monroe
Lucent Technologies