I am working on a HR application that needs the functionality to let employees book their on holidays for approval. I want this holiday to be tracked and to tie it to a certain number of days. For example, the maximum holidays per year is 30 days. How can I set up the holidays so that when a holiday is booked it takes that number of days away from the 30. I would also like a way of displaying hw many holiday days an employee has left.

Thanks!