I want to asign to all employees 10 days off that can be taken in a specific period, let's say 1st of July till 31st of July.

However, I want them to be sawn in the calendar view all year long (not just in July), so that they are able to request them in advance. 

Meaning I want those 10 days available to appear all year long here, next to those other 5 days available.

How can I do this?