Why would you want to do that? There doesn't seem to be any need to allow two different users to access the same cPanel account - why not share the one set of user details between more than one person? Or am I missing something (it's often the case).
you may upload your own copy of phpmyadmin to the Cpanel hosting account and configure it . This way, you may not need to use the phpmyadmin from the Cpanel and allowing both the user to login to the phpmyadmin