Find matches in column for identical positive and negative numbers

I don't think there is a MS office version 2403, please check and update your profile with the correct version. Different versions can use different formulas so it can be important to know which version you have.
now, are you looking for conditional formatting when you say "identify all cells" or are you looking for a simple count formula that would say there are this many cells that have negative values equal to the positive ones? Maybe you could follow the instructions at the top of the post for how to attach a sample workbook with enough information AND manually results so we could see?

Welcome to the forum.

Let's say you have -16, 16 and 16 in the list - should just a pair be picked up, or all three?

There are instructions at the top of the page explaining how to attach your sample workbook (yellow banner: HOW TO ATTACH YOUR SAMPLE WORKBOOK). Screenshots are of little practical use as we cannot manipulate them.

A good sample workbook has just 10-20 rows of representative data that has been desensitised. The sample layout accurately matches that of your real data. It also has expected results mocked up, worked examples where required, relevant cells highlighted and a few explanatory notes.

Administrative Note:

Is your forum profile showing the Excel PRODUCT that you need this to work for?

Members will tailor the solutions they offer to the Office PRODUCT (Excel, NOT Windows) that you have. Please check that your forum profile is up-to-date in this respect. If you aren't sure, in Excel go to File | Account and report what it says below the MS logo at the top of that page. If your product is for Mac, please also state this.

The three most recent Excel products are Excel 2019, Excel 2021 and MS365 - if you are using MS365, please give this name along with the version number in your profile (e.g. MS365 Version 2306). This is in the About Excel section further down the Account page.

Thanks.