I need to develop a tracking spreadsheet (for 19 employees) that will calculate accruing vacation time (on one worksheet) based on the following parameters:

Employees who have worked 2 years or less with the company:
- 3.75 hours biweekly (10 working days a year, earned at 5/6 of day for each full month)
Employees who have worked 3 or 4 years with the company:
- 4.5 hours biweekly (12 working days per year, earned at a rate of 1 day for each full month)
5 years and over with the company:
- 11.25 hours biweekly (15 working days per year, earned at a rate of 1-1/4 days for each full month)

In addition I need to be able to deduct vacation time used. Does anyone have any suggestions for layout or for a formula that can do part of these functions? I appreciate any advice!