Hi @Anonymous,
So you want to not create an item when the date is occupied, right?
You can use the Get items to check the current date whether is occupied. If the length of return value for Get items is not equal to 0, it means that this date is occupied, the Flow doesn't create an item.
For example:
addDays(variables('StartDate'), variables('NumberOfDay'),'yyyy-MM-dd')
length(body('Get_items')?['value'])

If so, the date field should formate:
addDays(variables('StartDate'), variables('NumberOfDay'),'yyyy-MM-dd')

Best Regards,
Community Support Team _ Lin Tu
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