[Exim] How to handle virtual domain mail differently

Hi,

Here's an odd question...
First the system details
Linux box running Debian
Exim 3.36.

I need to set up a a virtual domain on this box and handle the mail
for the virtual domain differently than the primary domain.

right now all mail handled by this box is delivered locally based on
this portion of the exim.conf

local_delivery:
driver = appendfile
group = mail
mode = 0660
mode_fail_narrower = false
envelope_to_add = true
return_path_add = true
file = /var/spool/mail/${local_part}


What I need to do is for the virtual domain each message must be
delivered
to a unique file name like this protion of a EXim4 conf defines.

domain_delivery:
driver = appendfile
directory = /var/mail/$domain/$local_part
delivery_date_add
envelope_to_add
return_path_add
directory_file = q-$tod_epoch-$inode.eml
initgroups = no
mode = 0666
mode_fail_narrower = no
check_group = no
check_owner = no


Is it ossible to handle the mail for a domain and a virtual domain
differently. Or do I need to convert the delivery for the primary
domain
to match what I need for the virutal domain.

BTW, upgrading the box to Exim 4 is not an option at this point.

Any pointers you can offer would be greatly apprciated.

Dean