How to prep test data by incrementing part of email addresses

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Hi,
I have a test data spreadsheet with hundreds of dummy email addresses in it. When my automation runs, it pulls each email address and creates a new user account from it. After I test my whole automation, I need to run the next test pass with new email addresses, since a user cannot sign up with an already registered email address. Below are three samples of the email data:

someone43@gmaill.com
somebody43@gmaill.com
something43@gmaill.com

After each run through of my automation, I want to increase the numerals by 1 in my data spreadsheet, to create “new” email addresses. So those cells will change to, and the next run will use, these new values for the email addresses:

someone44@gmaill.com
somebody44@gmaill.com
something44@gmaill.com

Since I first tested my automation, I have manually increased all of them one digit at a time, up to number 43, starting at number 1 – and I am so tired of doing it that I will give you my firstborn if you can help me.

FYI I am a citizen developer (in other words I am not a developer), so be gentle, please.

Thank you,
Val