!!!Excel VBA インターフェースを使う
http://www.ncfreak.com/magazine/No.003/vb_class.html

Base.cls
 Option Explicit
 
 Public Function getName() As String
     getName = "base class"
 End Function
Deliv.cls
 Option Explicit
 Implements Base
 
 Private Function Base_getName() As String
     Base_getName = "derived class"
 End Function
呼出
 Dim b As Base
 Set b = New Deliv
 Debug.Print b.getName
結果
 derived class

----
{{include_html banner_html, "!Excel"}}