Creating a zoom factor extension that works with a ToolbarControl
Extension\IZoomExtension.vb
' Copyright 2012 ESRI
' 
' All rights reserved under the copyright laws of the United States
' and applicable international laws, treaties, and conventions.
' 
' You may freely redistribute and use this sample code, with or
' without modification, provided you include the original copyright
' notice and use restrictions.
' 
' See the use restrictions.
' 

Option Explicit On 

'IZoomExtension interface
Public Interface IZoomExtension
    Property ZoomFactor() As Double
End Interface

Public Class myIZoomExtension
    Implements IZoomExtension

    Public Property ZoomFactor() As Double Implements IZoomExtension.ZoomFactor
        Get
        End Get
        Set(ByVal Value As Double)
        End Set
    End Property
End Class