module modMain
    Function main(ByVal cmdargs() As String) As Integer
        Dim lbLocal As Boolean = False ' toggle me !
        Try
            If lbLocal Then
                'Local test: generate error within main()
                Dim liI As Long = CLng(1 / liI)
            Else
                'Form test: generates error under button's event
                Dim goFrm As frmMain
                goFrm = New frmMain
                goFrm.ShowDialog()
            End If

        Catch ex As Exception
            ' This is not fired when lbLocal=FALSE in RELEASE version, but is fired in DEBUG version
            MsgBox(ex.ToString)
        End Try

        Return 0

    End Function
end module

Public Class frmMain

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
' Generates an error under button click event
        Dim liI As Long = CLng(1 / liI)
    End Sub
End Class