How to evaluate the answer of a multi-criterion formula by changing only one criterion?

[asadullahbutt911]

Example:
I have a very big sheet containing hundreds of rows having many calculations; each row containing calculation from preceding row for the calculation of the result at the 100th row. What I want to do is I want to calculate the value of 100th row (the answer) by changing only one parameter in, lets say, 70th row. I have to calculate the value of 100th row for 50 different values of the parameter at 70th row. Changing the value of 70th row, and copying the value of result at the 100th row for each value of the parameter would be tiresome. How can I do that using VBA code or a formula?

The calculations from 71st to 99th row are too long to be embedded in VBA code to be used as function. Is there any other way to do this? Please help!

 

[oldbrewer]

make a tiny small scale example eg 5 rows and post on here - it will be much clearer then.