Dim SumaTotal As Decimal = 0.0
Private Sub TextBox3_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
'Primero convertimos nuestros Textbox a decimales..
Try
SumaTotal =0
SumaTotal = CDec(TextBox1.Text) + CDec(TextBox2.Text) + CDec(TextBox3.Text)
'Ponemos el resultado de la suma :).
TextBox4.Text = SumaTotal.ToString()
Catch ex As Exception
MessageBox.Show(ex.Message,ex.Source)
End Try
End Sub