Public Interface IPlugIn
        ReadOnly Property Prop(ByVal Message As IPlugIn.Messages) As _
          PlugInProperties
        Function GetMessage(ByVal CopyOfMainWindow As Form, _
        ByVal Message As IPlugIn.Messages) As ReturnProperties
        Property Test() As ICommunication
    End Interface
Public Interface ICommunication
        Function ReceiveMessage(ByVal sender As IPlugIn, _
        ByVal message As IPlugIn.Messages)
    End Interface

Public Function GetMessage(ByVal CopyOfMainWindow As System.Windows.Forms.Form, _
  ByVal Message As IPlugIn.Messages) As IPlugIn.ReturnProperties Implements _
  IPlugIn.GetMessage
        If Message = Message.MyMenuItemClick And Not (IsNothing(Test)) Then
            Test.ReceiveMessage(Nothing, Nothing)
        End If
    End Function
Private _Test As ICommunication
    Public Property Test() As ICommunication Implements IPlugIn.Test
        Get
            Return _Test
        End Get
        Set(ByVal Value As ICommunication)
            _Test = Value
        End Set
    End Property

Implements ICommunication
Public Function ReceiveMessage(ByVal sender As IPlugIn, _
    ByVal message As IPlugIn.Messages) Implements ICommunication.ReceiveMessage
        MsgBox("Receive")
    End Function