Goal Seek - What if analysis - Excel

This can be used to determine a value required to achieve a goal.
   For example if you know the result or goal but don't know the input value to achive the goal.
   The goal needs to result from a formula, the input value of the formula is what we goal seek to find.

One example is a result/goal to pay off a loan 10 years early,  but we do not know the input value i.e. the value of the optional extra monthly payments to achieve this goal.

Goal seek can determine the input value to achieve the goal.

Worked example:
Using the loan amortization templete detailed in the previous post:

Set Cell - this is cell we want the result/goal to apply to
To Value - is the resulting value of the goal
By Changing - is the input cell that will achive the result/goal

Click ok to accept the answer and the values will be updated
Or click cancel to return