[Exim] Virtual Alias to file

Hi,

How do I do the following with exim.... I want a file /etc/exim/domain.co.uk
that i can add some forward information in for example.

chris@??? gets forwarded to chris@???

Also It need to rewrite the header so it comes from chris@??? as I do
not want it appearing as chris@???.

Any ideas....

Kind Regards,
Chris Bond