[exim] Opposite of ${time_interval:<string>} ?

Hi,

it seems that I need to convert "exim normal time format" into seconds but
I'm unable to find an expansion for this. What I need is exactly the
opposite of the ${time_interval:<string>} expansion:

    $ exim -be '${time_interval:123456}'
    1d10h17m36s

How can I convert "1d10h17m36s" into 123456 with exim? Although exim does
have a function for this (readconf_readtime), I'm unable to find an
expansion operator to convert as I demand.

Any ideas? Or wishlist?

Heiko

PS: Converting with an external perl script is easy but is not what I'm
    looking for.

Heiko Schlichting        | Freie Universität Berlin
heiko@???       | Zentraleinrichtung für Datenverarbeitung (ZEDAT)
Telefon +49 30 838-54327 | Fabeckstraße 32
Telefax +49 30 838454327 | 14195 Berlin