MSGSEP problem

Hi,
Don't ask me why but I have to deal with a separator which is :
---- COUPEZ ICI ---- CUT HERE ---- COUPEZ ICI ---- CUT HERE -------
With a white line before and a white line after.
How do I set my <MSGSEP> to deal with the whites lines (actually they are just CR)? I've tried a bunch of things and it doesn't work. The best, so far, are messages correctly separated but with no "subject", "date" and "from" fields.
How do I have to say "the separator is these three lines, two of them being blanks ?"

Erik BERNARD