I'd move it to google sheet, excel is the past, you can edit it from your phone, laptop, anywhere, no need to worry if you are not in front of the computer and you need to access or edit the calendar.
Second, i will create a littel tab with staff, name and # and position, this will allow you to have a vlook up and dropdown list, you only open the drop down, select the name, the employee number will be populated automatically, the same for off or PR, we can add dropdown list and some alerts in case you are missing anything.
With this calendar, you will never type again unless you need to add or remove an employee, everything else will be just with the mouse with a couple of clicks or from your phone just chossing from the dropdown options.
Let me know, this will take me 15 minutes top.