Envelope fields from body

Hi.
Here is short description of the project, I'd like to realize
via procmail.


     ------------    send           ----------------
     | Anyone ONE | ----------->    |   Anyone TWO | <-------|
     -------------    letter 1      -----------------        |
           ^                      letter2  | send            | letter 3
           |                               | via             |confirmation
           |                               | Re or Fw        |
           |                               |                 |
           |                              \|/                |
           |                          -----------------      |
           |                          | Autoresponder |------|
           |                          -----------------
           |    letter 4                   |
           <--------------------------------
                4 Send something from TWO


  Here is my question. Is there correct way to take right address "Anyone
ONE" from letter2 by procmail?
 May be it is stupid question, but this address should be into body of
letter2 and I don't understand how take an envelope fields from body of
letter. 

   Thanks


  Vladimir Dubnikov