Hi @C Mo,
Currently there is no such method to reach your requirement in SharePoint. A common workaround would be using Power Automate to check after the new event creation, delete the duplicate entry if any. Here is an example: Prevent double booking SharePoint calendar for the day.
In addition, there is a PowerApps Office Template named Book a Room that might do some help on this scenario. Reference: Office Template: Book a Room now available.
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