Sirs,
As mentioned above by one of my colleagues, there are many enterprises available in the market that you can purchase for your organization to handle work on your behalf. Just customize the leave rules, and it will work.
On the other hand, since you have requested an Excel format to be used, please find the attached Excel document for calculating leave for your organization.
However, please refer back to your human resources manual and apply your rules on entitlement, overtime, and carry-forward.
Regards