I don't think you need a calculation here unless you are using a line chart with a separate line for each year. Other than that you can just perform a find to limit your found set to the range of years you want to chart.
Do you want a line chart or will a bar chart serve here?
Hi Phil Line graph, two lines, one for minimum and one for maximum. Mitch
Ok, no calculation need then since you already have separate fields for each line.
If you have a single record for each year you can specify
a year field for the X axis
The Minimum field for one y axis series
Click the + button and add the maximum field as the 2nd y axis series
If you have multiple records per year with minimum and maximum defined as summary fields, you'll need to select "Use Data from current found set" and "show data points for groups of records when sorted". Then you'll need to sort your records by year to properly group your records for the chart.