Time Off Accrual Spreadsheet

Ok, so I'm not too advanced with Excel, can do simple things, but I need to be able to track on going time off by my employee's via a spreadsheet. Here's what I would like for it to do:

1. Name of Employee's down Column A
2. Bi-monthly dates across Row 2
3. Column "AA" is Total used that year
4. Column "AB" is what their balance remaining is for the year
5. If Column "AB" goes negative, number turns Red and bold

So basically if they took off 8 hours for the entire month of June, Column "AA" would show "8", Column "AB" would show much Paid Time Off they have left to use. If no time off is taken, then that number in Column "AB" would increase by the amount of Paid Time Off they are allowed to accrue based on company guidelines of say 5 hours each pay period.

I hope this is enough information on what I would like to accomplish. I tried searching the forums but have no idea where to start!

Thanks in advance for any and all help!