You might consider a database that tracks leave as though it were an item to be held in inventory. But instead of it having a supplier number, it has an employee number. And each employee has three or four different parts - sick, vacation, personal, comp, possibly others such as excused leaves for civic responsibility. Jury duty or military obligation due to reserve status. Make this as complex or as simple as you want. The issue will actually be easy because once you have at least three types of leave, you HAD to build it to allow as many types as you want.
Instead of having a "buyer" it has a user - the employee - who consumes it like an inventory item.
Instead of having "parts on hand" you have "hours on hand" for each employee - and the hours on hand subdivide according to type.
At any time, then, an employee's leave is simply the sum of all accruals minus the sum of all leave-taking of any flavor. You can implement this if you have two kinds of transactions... give leave, get leave. One has a net result of ADDING leave to the account. The other SUBTRACTS leave from the account. This isn't that hard to implement.
Now, if you wish to see all types of leave treated the same way for some reports, you just do your group-by one way. If you want to see details, you do the group-by differently.
Don't forget to use QUERIES instead of TABLES as report sources. You can do summations in queries so that you never have to store sums. And you can use the queries to show when an employee has a negative balance or a potentially negative balance. Your company policies will govern just how you treat such a case (allow negative balance in some categories, convert to LEAVE WITHOUT PAY in some categories, don't charge for leave in some cases - bereavement or civil obligation, for example.)
