Non Accruing vacation/sick time

Ok I need a formula that calculates vacation and sick time individualing. Employees automatically get 5 vacation days and 3 sick days every 6 months with and without rolling over. Is there a way to make it calculate automatically or do I have to go in and change the dates once a week or so? This is what it looks like now
Sick Days Sick Sick From To Available Used Left
Hire Date 6 Month Date Available Used Left
Smoe, Joe 11/3/2008 5/16/2014 16-Nov-2014 6 2 4 10 6 4
Baker, Cake 2/1/2002 1/1/2014 1-Jul-2014 3 3 0 5 5 0