IF you have this realtionship:
Employees::EmpID = VacationLog::EmpID
I've named the table you describe "vacationLog" and postulated a second table, Employees where you have one record for each employee. Employees::EmpID is an auto-entered serial number.
Then Sum ( VacationLog::Days )can be defined in Employees
to compute the total of all vacation days used for a given employee. This can also be modified to limit the total to just those used in a given year if a different relationship is used that matches on both EmpID and a year field.