Unique navigation for portfolio

I need to try implement a rather complex (to me) navigation for a portfolio. It needs to function like the portfolio navigation on this http://woodworthassociates.com/maine-audubon-1.php

(See bottom right of photo)

Each portfolio section has circles for each image in that section. The < and > navigate between those images, but once the end of each section is reached the > sends them to the next section so that the flow is continuous.

Currently we are creating a page for each portfolio image and we are creating the navigation manually on each page. Going to be a nightmare to update or change things around if we need to.

Anyone got a better idea how to handle?