[Exim] return-path rewriting

Hi all

I'm runnig exim4 and still trying to rewrite return-path headers, without
success. Using trusted_users directive I could avoid Sender header, but not
return-path. I would like to rewrite this header depending on mutt folder-hook,
is this possible on exim4? Could you please tell me how?

thanks in advance and sorry for my english

apt-regards

-ejg