PPPoE schedule daily reset

Hi,

Maybe someone allready asked this question before, but I can't seem to
find it... I know some fritzboxes have these function.
Our DSL provider resets the DSL connection every 36 hours (and 4 minutes).
Because I have no control (except for reconnecting myself at a certain
time - start counting from that)... I would like to schedule the PPPoE
going down at 4 AM, and immediately going back up.
That way DYNDNS has it's time to reregister my IP-address, and after
that my VPN's can come up rightfully.

Now when a hard reset comes from my ISP, I have to wait several
minutes before my DYNDNS is renewed at the other site, and only after
that time the VPN will come back up...
I thought there was a CRON in monowall, but how would that rule look ?

Kind regards,
Michel