well u can set up a domain to use this
for instance...
www.whatever.com
inside the httpdocs directory create a folder called myadmin
set the folder permission in plesk to be password protected directory
upload phpmyadmin via ftp
create a config.inc.php to suit your needs
give the url to trusted clients or people.. give them username and password to protected directory...
give them auth via the config.inc.php
wallah u can use latest version of phpadmin
but for securing access to the box abit more
if you have root access to the box (which you should if your doing this in the first place) create a user with admin rights to the box and change his group access to a non superuser add this into the config.inc.php as your main account that can access the databases on the box.. then u don't need to worry about anyone getting into your system with your personal details or admin but can allow them to edit the the db...
let me know if this helps..
-Mike