Block a specific timeframe when adding new entries to a Modern SharePoint Calendar

I am trying to block the timeframe 11AM-12PM so users won’t be able to select it when adding new entries to a modern SharePoint calendar. I can’t find anything online that can point me in the right direction, and I am wondering if it’s even possible to do.

The only way I can think of getting this done is through a workflow, where the user will receive an email to resubmit their entry outside of that timeframe and then delete the current entry. I am hoping there is a better approach to this.

Any advice will be appreciated.