Macro to calculate the percent difference after entering an input

Hi all,

I'm currently working on a spreadsheet for engineering purposes.

Basically, I input the first value as shown in A1. Then I have to guess a value in A3 and adjust it until the percent difference between A6 and A7 is matched with an accepted value, which I want to be as close to zero as possible. A6 and A7 are linked with their own formula elsewhere on the spreadsheet and are dependent on the values of A1 and A3. A4 is dependent on both inputs and is just a difference between the inputs (A1-A3).

I know I can do this with the "Goal Seek" function in Excel. However, I've tried it a few times and after many iterations it could not find a value that is close to my tolerance of 0.0001 or as close to zero as possible.

I can keep on guessing a value in A3, but it takes a while and can be time consuming.

Is there a way to automate this process? Basically, I want to input a value into A3 that gives me a percent difference as close to zero as possible.

Thanks!

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Cross posted here: http://www.ozgrid.com/forum/showthread.php?t=166682

What's in A6, A7, and C6?

I apologize for cross posting. I've requested the other thread to be deleted.

A6 and A7 are outputs from calculations done on the same sheet and are dependent upon the data in A3 and A4. C6 is merged with the cell below it, which is the calculation of the percent difference between A6 and A7.

The formula I used for percent difference is (ABS((A6-A7))/((A6+A7)/2))*100

Unfortunately, I am not able to post the full spreadsheet on here due to company policy.

Basically, I want to make C6 (percent difference) to be as close to zero as possible, or at least 0.001 or something. In order to do this, I need to adjust A3 many times in order to get this. Many times, I just guess to only 2 decimal places, but I would like a more precise answer. I would just like to automate this process with some sort of macro or iteration, sort of similar to Goal Seek.

There are no parameters to GoalSeek that control the precision of the result. You could try Solver instead, which does have several parameters.

Without knowing what's happening in A6 and A7, I have no further suggestion.