[Exim] SMTP error code in bounce messages

Hi,

I would like to generate custom fields in
bounce messages, based on remote mta smtp
response code.

I am using bounce_message_file -option and
have $h_xxxx -evals to copy/generate headers based
on original message.

But I still need to add custom headers based
on remote MTA SMTP-response code, something like
(not in exim notation:):

x-remote-error: if (smtperror == 552) { "remote mailer over quota" }
                    else { "unknown error" }

I hope you can catch the idea from that.

I quick peek to expand.c&manuals didn't reveal
anything, if this can be done or the is such variable.

The error code and text appears at bounce body
in 'following address caused the failure:' -section
but that is wrong place for my application
because I need to evaluate the code and build
error message according the code.

So any hints if such thing can be tweaked into standard
exim?

BR, Jori