Dear @Aurelia Lyons / Student of Davidson High,
Thank you for posting your question in the Microsoft Q&A forum.
Unfortunately, it is not currently possible to add custom error bars in the Excel 365 Web App. The custom error bars option is only available in the desktop version of Excel.
In the meantime, please confirm which license you are using by following these steps:
- Go to https://www.office.com and sign in.
- Click your profile icon > My Microsoft 365 profile
- Look for Subscription > View subscriptions.
Once you provide this information, we can confirm on whether your current license allows the desktop app or if an upgrade is needed.
Following this, Microsoft donates Office 365 A1, including web and AI tools, at no cost to eligible institutions. However, this plan does not include the desktop app.
Alternatively, you can use a personal account and purchase a license that allows use of the desktop apps, such as Microsoft 365 Personal Buy Microsoft 365 Personal (formerly Office 365) - Subscription Price | Microsoft Store
I hope information above helpful and meet your expectation, if you have any other questions, please feel free to reach out.
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