[exim] Force routing by adding custom header

Is it possible to configure exim to use a specific routing option by
setting a custom header value?

So, for example, within the email headers having something like:

From: address@???
To: address@???
EximRoute: use.this.server.com

Where the value in the EximRoute (or whatever header...) would be used
as a manualroute option for this message. It would always only contain a
single server name, and it would always be used as manualroute bydns.
The header would be stripped out before forwarding the message on.

If there are any delivery errors etc causing the message to be queued,
then any retries must still be sent via the specified route.

If no 'EximRoute' header is present, then just route the message as normal.

The exim server would only be accepting requests from a locally running
application, no external access to the server would be possible.