extract header from current message (to pass to shell)?

[Marianne Promberger <marianne.promberger@xxxxxxxxx>]

Is it possible to extract a specific message header from mutt and pass
it on to a shell command? maybe by passing the current message to
formail (but then, what would I write for "the current message" on
mutt's shell command prompt that comes up when I press "!" ?)

Background:

I'd like to be able to "ignore" threads that are of no interest to me
(on mailing lists), and I'm currently thinking about this:

(a) bind a key to delete the current message and also extract the
message ID and append it to a textfile (this is where I'm stuck) 

(b) set up a folder hook to delete-pattern messages that are "In reply
to:" messages with IDs that are in the textfile from (a) (I think I've
got that part sorted)

Thanks,
m.