Procmail filter if more than a certain number of messages

Hi,

How can I make a procmail rule that will only run if I already have
more than a certain number of messages (in my mail spool)?

I am running on Linux and have "mailutil check" available, as well as
the basic unix utilities, so I can probably dream up a command that
can return any appropriate value (eg "yes" or "no") depending on the
number of messages. But I can't see how to use that to control
procmail.

Any tips? I've searched around, but not found anything in a FAQ or
man page.

Thanks,
Andrew

Re: Procmail filter if more than a certain number of messages

OK; I got this working using the man pages and http://pm-doc.sourceforge.net/pm-tips.html

I've posted a description at http://www.acooke.org/cute/DroppingLe0.html

Andrew