I've created a spreadsheet to track my weight and my BMI readings (for
health (diabetes) and not vanity.

I'd like the Y axis of my chart to show two values/lines across the chart
indicating the lower and upper target range of my BMI reading. I know that
my weight won't flutuate so quickly to stand out against these ranges but
its the kind of aesthetic touch I like to add to my charts.

Thanks if you can help.

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It's a 106 miles to Chicago. We got a full tank of gas, half a pack of
cigarettes, it's dark and we're wearing sunglasses.