[Exim] rewriting header with alias address...

Just a little question.
I use virtual domains (which seem to work correctly...).
I would like to rewrite the header lines from the mail send to an alias
with the alias address
in place of the real address (which appear actually).
I presume, i must to use a specific command in the received_header_text
command...
I use actually:
${if def:received_for{\n\tfor <received_for>}}

Below, you can find an example of the actual header of an email send to
webmaster@???.
"webmaster" is an alias for "user1" on the mail server "mail.domain.com".
The problem is the 3th line...

Received: from  XXX.X.XX.XXX by mail.domain.com with scanned-ok
     id 17bLHT-0001de-00
     for <user1@???>; Sun, 04 Aug 2002 15:18:47 +0200
Received: from XXX.X.XX.XXX (helo=mel-rto4.wanadoo.fr)
     by mail.domain.net with esmtp Exim
     id 17bLHS-0001ay-00
     for <webmaster@???>; Sun, 04 Aug 2002 15:18:46 +0200
Received: from mel-rta10.wanadoo.fr ( XXX.X.XX.XXX ) by
mel-rto4.wanadoo.fr (6.5.007)
     id 3D49FD32000CEC4F; Sun, 4 Aug 2002 14:21:01 +0200
Received: from myStation (YYY.Y.YY.YYY) by mel-rta10.wanadoo.fr (6.5.007)
     id 3D49FFDD000CC5F7; Sun, 4 Aug 2002 14:21:01 +0200
Message-ID: <002501c23bb2$257d95c0$0100a8c0@???>
From: "user.test@???>
To: <webmaster@???

Thank's for all...