If I were to have data in excel just like the table below, and then make line charts with that data.
All is well and good until I have to come back around and add rounds 11, 12, and 13 to the data.
If you skip rows or columns, this technique won't work as expected. Because the chart defaults will use the label headings in each column for each series name, you can't use those labels to name the dynamic ranges.
You might be wondering why I added the Series label to each range name. Don't use the same labels for both your spreadsheet headings and your dynamic range names. If you enter new data, the chart won't yet reflect it. Next, update the chart's axis labels (column A), as follows: You don't have to update February; Excel does that for you.
By default, Microsoft Excel automatically updates a chart when you make a change to the chart data.