I have a spreadsheet that I'd like ot recreate the capability. I can
Copy/Pasteand retain the capability but I don't know how to create it.
Chart Effect:
When plotting ongoing data in a run (line chart) with dates on the x-axis
going into the future, the series will drop to zero at the end of the current
data. I'd like the series to just end at the last data point. The chart is
question does this.
Spreadsheet Method:
In a typical data table, the series is calculated from two other cells,
taking a ratio. When there is no data the #DIV/0 error appears. In the
spreadsheet in question, there is no formula in the last cells of the table,
hidden values or formulas is not turned on, but when data is entered at the
bottom of the table, the formula automatically fills in and the chart
updates. The formula appears as if it were Copy/Pasted. The remainder of
the table is blank. There are no Macros in the sheet.

How is this accomplished?