Sorry I couldn't respond faster! I have been out of town!
I will assume you have Office 2000 for these instructions:
Go to the chart and hold your mouse over one of the data points and right click. Then click "Source Data" and go to the "Series" tab. On the bottom left you should see a list box that contains "deer times, sunrise, sunset, etc." Click on which ever item you want to change. After you click on the item in the list box that you want to change, the combo boxes to the right should contain the cell ranges for the X and Y values of the chart. Click on the icon to the right of the X or Y values and it should go to the sheet that contains the data. Also a small window will appear where you can manually modify the ranges.