A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hello Corinne G. Welcome to the Microsoft Community.I understand that you are having problems with Excel after replacing your mouse. I fully understand your confusion.Since you mentioned that the problem doesn't occur after you replaced it with your old mouse, then it means that the problem is related to your new mouse, and there might be some driver conflict, you can visit your mouse brand's official website to check if there is any driver update or troubleshooting solution available.
Hope the above information is helpful to you. Best RegardsEliac | Microsoft Community Support Specialist