Type Level1_t
  Offset As Integer
End Type

Private Enum Level2_Mode_t
  Typ
  TL
End Enum

Private Type Level2_t
  Offset As Integer
  Mode As Level2_Mode_t
End Type

Private Type Level3_t
  Offsets As Collection
End Type

Private Type Structure_t
  Level1 As Level1_t
  Level2 As Collection
  Level3 As Collection
End Type

Private Function Structure_f(Structure As Structure_t, _
                             Workspace As Range, _
                             Offset As Integer) As Structure_t
End Function

Private Sub Worksheet_Change(ByVal Target As Range)
  'Dim Structure As Structure_t
  'Set Structure.Level2 = New Collection
  'Set Structure.Level3 = New Collection

  ' ...

  Dim Workspace As Range
  Set Workspace = Workspace_f(Target)

  Structure = Structure_f(Structure, Workspace, Offset)