Hi
Thre is no otherway we can assign values to prior years. Even if you refer years as variables you can't attach them to chart.
Ex :
Numbervar Y_2005 := 10;
Numbervar Y_2006 := 20;
Numbervar Y_2007 := 30;
Now if you use if statement to bring these values into your formula like :
If Y_2005 = 10 then 'Year 2005' Else
if Y_2006 = 20 then 'Year 2006' Else... so..on..
Here the 'IF' statement will execute always once because Y_2005 is always 10 and it will not evaluate other conditons.. so, you will not get these values into your formula to show on your chart.
Only excel is the best way to complete the task