一个类的属性如何在另一个类的属性更新时更新？

Question

假设您有以下三个类：

Public Class SpecialJob : Inherits Job
   Public Property Details As List(Of Detail)
   Public Property JobTotals As Totals
End Class

Public Class SpecialDetail : Inherits Detail
   Public Property DetailTotals As Totals
   Public Property DocNum As String
   Public Property Reference As String
End Class

Public Class Totals
   Public Property Expense As Decimal
      Get
         Return tExpense
      End Get
      Set(value As Decimal)
         TotalExpense -= tExpense
         tExpense = value
         TotalExpense += tExpense
      End Set
   End Property

   Public Property Tax As Decimal
      Get
         Return tTax
      End Get
      Set(value As Decimal)
         TotalExpense -= tTax
         tTax = value
         TotalExpense += tTax
      End Set
   End Property

   Public Property TotalExpense As Decimal
End Class

如何实现解决方案，以便更新Detail类的费用也会更新Job类的费用？

编辑： 每个类中还有许多其他属性和功能。我只用了几个来展示基本结构。