[boudyonline]

جرب الكود كالآتي :

كود :

Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged
       TextBox3.Text = Val(TextBox1.Text) + Val(TextBox2.Text)
   End Sub

   Private Sub TextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
       TextBox3.Text = Val(TextBox1.Text) + Val(TextBox2.Text)
   End Sub