Yes, this can be done using our User Panel. The panel allows the ability to make payments when any amount remains due, or to make changes or cancellations (if you have those enabled for the event). To use this, you'll need to have the users login. You can force them to login prior to registering, or at least enable the auto-user creation feature so they can create a login account at the same time as registering for the event.
Create a menu item (Registered access level) for DT Register -> User Panel. Instruct your users (in the thanks email they receive after registering) how to make additional payments and provide a link if desired. Thanks.