HE has a web page script for that.....https://ipv4.tunnelbroker.net/nic/update?hostname=_TUNNEL_NUMBER_
It will then ask for your ID and PW. Upon success, it will display the IPv4 address and either "good" or "nochg".
Although the URL could have your ID and PW in it, I chose not to.
Search for "/nic/update?hostname=" and you will find 6 results for 5 other threads on this topic.
If you bookmark it, and then click on it via your web browser (or if using any Unix based OS, use wget with the URL in your boot script), then you will update. The wget method will need the ID/PW in the URL.