Creating Nested Class

I am trying to create a nested class in VBA.

So far I have successfully created the following:

OurCompany.Department.Employee("John")

How can I create a few groups of Department so I can store the data seperately. Something like this

OurCompany.Department("Finance").Employee("John") = "Employee Number 100"
OurCompany.Department("Finance").Employee("Kim") = "Employee Number 101"
OurCompany.Department("Engineering").Employee("Sam") = "Employee Number 124"

cDeparment Class

Private pDepartmentEmployee As Collection
Public Property Get Department(RefString As String) As cEmployee

    Set Department = pDepartment.Item(RefString)

End Property

Public Property Set Department(RefString As String, ByVal objDepartEmployee As cEmployee)

    pDepartmentEmployee.Add objDepartEmployee, RefString

End Property

cEmployee Class

Private pEmployee As Collection
Public Property Get Employee(RefKey As String) As String

    Employee = pEmployee.Item(RefKey)

End Property

Public Property Let Employee(RefKey As String, RefItem As String)

    pEmployee.Add Item:=RefItem, Key:=RefKey

End Property