I need to be able to reference the equation of the trend line obtained on a graph in Microsoft Excel 2007.

I know I can just type the equation but my instructor would like the whole process to be automatic. Just change the values and everything should change with it. Including data which relies on the Equation of the Trend Line.

Any ideas to help me here?


Lastly the equation comes in this pattern Y = aX + b, where X is known, a and b are numbers taken from the trend line. If I can reference from the chart how can I make it so that it will solve the Y automatically given a value of X. Because if I do reference the equation the whole equation will appear. But i want the Y to be solved automatically.