Progress bar that works forwards and backwards

I seem to have the complete opposite problem. in theory, just because they go backwards, doesn't mean they don't have a higher completion in general due to using the previous button after having already completed future sections. So we want our progress to show the true progress even if they go back to review a previous section. 

I viewed previously shared solution (Allison) and thought it was great. I was about to implement her solution, when my manager cautioned me on two things: 1. for someone who uses the previous button and reviews sections already completed (which also occurs for the LMS testing/review teams), the variable used shows the progress of that previously viewed section which appears to have progressed backwards. 2. For ADA compliance, we build every course with extensive effort for a user that's using a screen reader. The reader reads the %completion of the current visited section, even if they already completed it and moved past it. When they revisit using the previous button, even if they've already completed sections ahead, it shows a lower percentage of progress. This occurred even when one of our top designers used a javascript solution which worked wonderfully to combat problem #1 above. However, the ADA reader read the percentage pertinent to already visited section they've returned to. We don't seem to have a dynamic solution which handles these issues, so we continue to use a state change and triggers on a rectangle shape on our course section slides. July 25 is a A360 webinar on this topic and will be interested to see if any other solutions come across.