[exim] retry times from dbm

Hej,

I was planning to use a dbm file to store maximum retry times for
various domains. Now I realise this may not be as easy as I thought, as
retry rules are not expanded.
Does anybody know a trick or hack to accomplish this? I could probably
live with limitation to a small set of retry times (like 4, 7, 14, 30,
60 days.) but I fear that won't help much.

IMHO the following examples would be quite intuitive, but obviously
don't work:

* * F,${lookup{$domain}dbm{foo.dbm}}d,1h

and

${if eq {${lookup{$domain}dbm{foo.dbm}}}{4}{$domain}{no}} * F,4d,1h
...

I just realised the easiest way to accomplish what I need might be to
include an extra file into exims config that just contains retry lines,
and tell my script to update this file in addition to the dbm.

Any thoughts are welcome.

lg,
daniel