Duplicated invoices in Sharepoint library

Hello everyone,

I have tried to build an automation in a Sharepoint library to identify when a supplier is using an invoice number that they have used before. I have created a calculated column that concatenates the name+invoice number to be able to identify the duplicates, however, I cannot find how I can then make the library or Power Automate notify me when a duplicate is spotted as calculated fields seem to be tricky to query. Can I create a Power automate flow that can do that?

Thank you for any advice you could give me.

Thanks