look in one of these under /etc/
cron.d
cron.daily
cron.hourly
cron.monthly
cron.weekly
in mine it was in cron.weekly
you should find refresh-ddns , move it to hourly
mv /etc/cron.weekly/refresh-ddns /etc/cron.hourly/
and that should update it every hour.
I haven't tried it yet, i just found out about it, i'll try it today though when i get home, and let you know how it goes
hope that helps
Cheers
(edit)
Not sure but i think a service would need to be restarted for this to take effect, you could restart e-smith , maybe someone else might have a better idea.
and then if it works i can put together my first how to

woo hoo moving up in life
(end edit)