Here's what I want to do:
I've composed a mail in mutt. Now I want to add an attachement by executing a script which prints a path, which is the file which should be attached.
I want to be able to do this from within mutt.
Use-case: Add a iCal/vCard as attachement which is selected by script (which then exports it from my calendar/addressbook, saves it in a file and reports this file back to mutt, which adds it as attachement.