Dynamic Deviation line anchor to latest populated day, not a fixed date

I am working with an Intelligence Sheet line chart backed by live data that updates daily. I want a deviation line that always compares today (the latest populated day) against the same day last year, and updates automatically as new data lands each day.

When I add a deviation line referencing "today," it locks to the specific day it was plotted on rather than following the newest day in the data. So the next day, the line still points at the original date instead of moving forward with the latest data.

Thanks!