Connect to PostgreSQL server from an ADSL connection

Hi all,

I am writing because I would like to know that how can I connect
remotely to a PostgreSQL database from an ADSL connection, which has
different IP address every time when it connects to the Internet. This
ADSL connection is registered to www.dyndns.org, so its dynamic IP
address is replaceable with the registered domain name.
My problem is the changing IP address: I would not like to modify the
pg_hba.conf file every time when the remote computer's IP address
changes. I know that there is the "listen_addresses" parameter in the
postgresql.conf file, which can have not only IP addresses as value
but domain names also, and it is required for remote connections. But
in the pg_hba.conf file - as far as I know - I can not use domain
names only IP addresses, so it seems to me that I can not push the
advantage of registered domain name at dyndns.org.
Is there any way to configure the PostgreSQL server to accept remote
connection from one (but always the same) computer which has dynamic
IP address?

Thank you in advance,
Szabolcs

p.s.: Sorry for my bad English... If something is not clear, I will
try to explain it more detailed.