Using What-If Analysis, you can visualize the effects of different variables, making it easier to assess risks and opportunities. In Excel, three primary tools are available for performing What-If ...

Go to Data, click the dropdown arrow next to What-if Analysis, and choose Goal Seek. Select cell B5 for Set cell, as this is the cell that will contain the total retirement savings you want to reach.

Next, have Excel run the regression on the two columns of return data you generated. Under the Data menu, the Data Analysis button allows you to select Regression.