[Excel] How to make a line chart with a horizontal highlight

Horizontal highlights help identifying periods outside an expected band of variation.

In this example minimum and maximum values are hardcoded, but you can use formulas to create dynamic bands based on the data, dates or external parameters.
If you use overlapping areas the first series must be white (or background color) to simulate the band above. You also have to define the maximum value.
Stacked areas look better, because the bottom one can be fully transparent (no fill), so the gridlines remain visible. The maximum value is defined by band width.