Excel 2007 : How do you get the X-Axis in a chart to update automatically?

I have a chart that I would like to automate. It shows an account balance growing at different interest rates. Along the X-axis is the person's age. I have a cell that is the investment period. I would like the chart to only show that person's age along the x-axis for the given investment period. I know how to change the chart manually each time I change the investment period, but is there a way to make it update automatically?

Thanks in advance!