Fix Excel Rolling Line Graph

My current Excel workbook tracks a 12-month rolling set of figures, yet the line graph that should visualise those numbers has stopped updating whenever I add a new month. I need the chart repaired—or rebuilt—so it automatically displays the latest twelve data points without any manual range adjustments and without disturbing the existing data layout.

Here’s the flow I’m after: I enter the newest figure, hit save, and the line graph instantly refreshes while the oldest thirteenth point drops off. If reshaping the source into an Excel Table, adding dynamic named ranges (OFFSET/INDEX), or even a light VBA snippet is the cleanest route, that’s perfectly fine; the key is that the end result remains an ordinary .xlsx I can maintain myself. there are several data tabs to fix

Deliverables
• An updated spreadsheet containing a fully functional, dynamic line graph that always shows the most recent 12 months of data.
• A short, in-file note (or separate sheet) outlining the formulas, named ranges, or code you used so I can edit or extend it later.

Acceptance test: after I paste a new monthly value, the chart immediately reflects the change and the data it visualises stays accurate.