Progress bar in Articulate Storyline: Easy solution, using only one built-in variable

I viewed Allison's approach at length yesterday 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 previously completed sections if they revisit using the previous button, even if they've already completed sections ahead. This occurred even when one of our top designers used a javascript solution which worked iwonderfully to combat problem 1. above. However, the ADA reader read the percentage pertinent to already visited section. We don't seem to have a dynamic solution which handles these issues, so we opted to use a state change and triggers on a rectangle shape on our course section slides.