Set each of the projects' Root Namespace to "ExceptionsDemoNS"
Create three projects
Set Console Ap as startup project
Because each math Class is in a differant assemble the client will indicate
the source of the error by Assembly name.

   ex.Source will show

'1... VB Console Application Project "MathErrorClient" 

Module MathErrorClient
    Sub Main()
        Dim oMath1 As New ExceptionsDemoNS.MathClass1
        Dim oMath2 As New ExceptionsDemoNS.MathClass2
        Dim strAnswer As String
        Console.WriteLine("Starting...")
        Try
            strAnswer = oMath1.Add(255, 2)
            Console.WriteLine("Answer 1 = " & strAnswer)
        Catch ex As Exception
            Console.WriteLine("1... Source: " & ex.Source)
        End Try

        Try
            strAnswer = oMath2.Add(255, 2)
            Console.WriteLine("Answer 2 = " & strAnswer)
        Catch ex As Exception
            Console.WriteLine("2... Source: " & ex.Source)
        End Try
        Console.ReadLine()
    End Sub
End Module

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'2.... VB Class Library Project "MathClass1" 

Public Class MathClass1
    Public Function Add(ByVal X As Byte, ByVal Y As Byte) As String
        Dim bAnswer As Byte
        bAnswer = X + Y
        Return bAnswer.ToString
    End Function
End Class

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'3.... VB Class Library Project "MathClass2" 

Public Class MathClass2
    Public Function Add(ByVal X As Byte, ByVal Y As Byte) As String
        Dim bAnswer As Byte
        bAnswer = X + Y
        Return bAnswer.ToString
    End Function
End Class