Making one cell subtract from another cell and insert result in a 3rd cell.

Unfortunately I have zero experience with Macros which may be required.

I'm doing some personal financial work and am hoping I can get some help to automate for which I would be very grateful.

1) The first thing I would like to do is:

When there is a figure in Column P (beginning with P3), subtract that number from the figure in Column AB one Row earlier and insert the result in Column AB in the same row as the Column P figure.

E.g., in this workbook the first time there is a figure in Column P is P5.
Subtract the figure in P5 from AB4 and insert the result in AB5.

The next figure in Column P is P7.
Subtract the figure in P7 from the figure in AB6 and insert the result in AB7.
Etc.

It would be ideal if it would not do anything until there is a figure in Column AB. Eventually there will be but I'm proceeding Row by Row.
I.e., the Column P figures are all already in that Column.
The Column AB figures are not there. When I work on Row 3 I insert a figure into AB3, when working on Row 4 I insert a figure into AB4, etc.

It would be less confusing if the subtraction did not activate until cued by the insertion of a figure into the AB Column (as opposed to inserting negative numbers in the AB Column at first).

Would a Formula work for this or does it need a Macro?

Thank you.

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Attach a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

Click on GO ADVANCED and then scroll down to Manage Attachments to open the upload window.

Assuming that column O is also already populated before the values are added to column AB try pasting the following in AB4 and dragging the fill handle down to AB17:

Formula:

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Let us know if you have any questions.

Thank you very much for responding and for your work.

Do I clear all the existing figures in Column AB and replace the ones that I've cleared after I cut and past/drag fill handle?

You're Welcome and thank you for the feedback.
Working from the 'After' workbook, you could either clear the figures and paste/drag starting with AB4 or leave what you already have and paste the following modification of the formula into AB18:

Formula:

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I hope that you have a blessed day.

Originally Posted by JeteMc

You're Welcome and thank you for the feedback.
Working from the 'After' workbook, you could either clear the figures and paste/drag starting with AB4 or leave what you already have and paste the following modification of the formula into AB18:

Formula:

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In the event that this resolves issues, please take a moment to mark the thread as 'Solved' using the thread tools drop down on the ribbon above your first post.
I hope that you have a blessed day.

Thank you, will try that.

I've now posted the entire project of which this is a part here:
https://www.excelforum.com/excel-pro...-3rd-cell.html

Post #9.

(After posting here initially I thought that it wouldn't be possible without Macros and posted over there also].

Thread closed in favour of the one in the VBA section.