Version neutral PIA's - of a more up to date variety

    Private _value As String = ""
    Private Const notSet As String = "not set"

    Public Property MyProperty() As String
        Get
            If String.IsNullOrEmpty(_value) Then
                Return notSet
            Else
                Return _value
            End If
        End Get
        Set(ByVal value As String)
            System.Windows.Forms.MessageBox.Show("MyProperty Set has been called", "MyAddin356")
            _value = value
        End Set
    End Property

    Public Sub MySub()
        System.Windows.Forms.MessageBox.Show("MySub has been called", "MyAddin356")
    End Sub

    Public Sub MySubWithParameter(ByVal aParameter As String)
        _value = aParameter
        System.Windows.Forms.MessageBox.Show("MySub2 has been called; _value is '" + _value + "'", "MyAddin356")
    End Sub

    Public Function MyFunction(ByVal aParameter As String) As String
        _value = aParameter
        Return _value
    End Function

    Private myOtherAddin As String = "MyAddin356.AddinModule"

    Private Function GetAddinObject(ByVal progID As String) As Object
        Dim Addin As Office.COMAddIn = OutlookApp.COMAddIns.Item(progID)
        If Addin IsNot Nothing Then
            Dim AddinObj As Object = Addin.Object
            If Addin.Connect Then
                Return AddinObj
            End If
        End If
        Return Nothing
    End Function

    Private Sub btnPropertyGet_Click(ByVal sender As System.Object) Handles btnPropertyGet.Click
        Dim AddinObj As Object = GetAddinObject(myOtherAddin)
        If AddinObj IsNot Nothing Then
            Try
                Dim returnValue As Object = _
                    AddinObj.GetType().InvokeMember("MyProperty", Reflection.BindingFlags.GetProperty, Nothing, AddinObj, Nothing)
                System.Windows.Forms.MessageBox.Show("MyProperty returned " + returnValue.ToString(), "MyAddin357")
            Catch ex As Exception
                System.Windows.Forms.MessageBox.Show("btnPropertyGet_Click. Error:" + ex.Message, "MyAddin357")
            End Try
        End If
    End Sub

    Private Sub btnPropertySet_Click(ByVal sender As System.Object) Handles btnPropertySet.Click
        Dim AddinObj As Object = GetAddinObject(myOtherAddin)
        If AddinObj IsNot Nothing Then
            Try
                Dim parameter As String = AdxCommandBarEdit1.Text
                AddinObj.GetType().InvokeMember("MyProperty", BindingFlags.SetProperty, Nothing, AddinObj, New Object() {parameter})
            Catch ex As Exception
                System.Windows.Forms.MessageBox.Show("btnPropertySet_Click. Error:" + ex.Message, "MyAddin357")
            End Try
        End If
    End Sub

    Private Sub btnCallSub_Click(ByVal sender As System.Object) Handles btnCallSub.Click
        Dim AddinObj As Object = GetAddinObject(myOtherAddin)
        If AddinObj IsNot Nothing Then
            Try
                AddinObj.GetType().InvokeMember("MySub", Reflection.BindingFlags.InvokeMethod, Nothing, AddinObj, Nothing)
            Catch ex As Exception
                System.Windows.Forms.MessageBox.Show("btnCallSub_Click. Error:" + ex.Message, "MyAddin357")
            End Try
        End If
    End Sub

    Private Sub btnCallSubWithParameter_Click(ByVal sender As System.Object) Handles btnCallSubWithParameter.Click
        Dim AddinObj As Object = GetAddinObject(myOtherAddin)
        If AddinObj IsNot Nothing Then
            Try
                Dim parameter As String = AdxCommandBarEdit1.Text
                AddinObj.GetType().InvokeMember("MySubWithParameter", Reflection.BindingFlags.InvokeMethod, Nothing, AddinObj, New Object() {parameter})
            Catch ex As Exception
                System.Windows.Forms.MessageBox.Show("btnCallSubWithParameter_Click. Error:" + ex.Message, "MyAddin357")
            End Try
        End If
    End Sub

    Private Sub btnCallFunction_Click(ByVal sender As System.Object) Handles btnCallFunction.Click
        Dim AddinObj As Object = GetAddinObject(myOtherAddin)
        If AddinObj IsNot Nothing Then
            Try
                Dim parameter As String = AdxCommandBarEdit1.Text
                Dim returnValue As Object = _
                    AddinObj.GetType().InvokeMember("MyFunction", Reflection.BindingFlags.InvokeMethod, Nothing, AddinObj, New Object() {parameter})
                System.Windows.Forms.MessageBox.Show("MyFunction returned " + returnValue.ToString(), "MyAddin357")
            Catch ex As Exception
                System.Windows.Forms.MessageBox.Show("btnCallFunction_Click. Error:" + ex.Message, "MyAddin357")
            End Try
        End If
    End Sub