I created two fields in the hr.leave.allocation model called x_date_range_from  and x_date_range_to, the purpose behind this is to restrict the particular employee to request time off outside particular date range (I know there is validity on the time off type, but I want for a particular employee)...

Now I need to create an automated action on the ODOO13, that if someone tries to select the date_from and date_to from the hr.leave model, it should raise a warning,'the leave should be selected within the range'

How do I create automation for the same?