Public Class Case3
    Dim QtyComputer, QtySpeaker, QtyKeyboard, Total As Integer
    Dim strComputer, strSpeaker, strKeyboard As String

    Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
        Select Case cmbProduct.Text
            Case "Computer"
                QtyComputer += txtQuantity.Text
                strComputer = QtyComputer.ToString()
                txtSaved.Text += cmbProduct.Text + ", " + strComputer
            Case "Speaker"
                QtySpeaker = txtQuantity.Text
                strSpeaker = QtySpeaker.ToString()
                txtSaved.Text += cmbProduct.Text + ", " + strSpeaker
            Case "Keyboard"
                QtyKeyboard = txtQuantity.Text
                strKeyboard = QtyKeyboard.ToString()
                txtSaved.Text += cmbProduct.Text + ", " + strKeyboard
        End Select
    End Sub

    Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
        Total = (QtyComputer * lblComputerPrice.Text) + (QtyKeyboard * lblKeyboardPrice.Text) + (QtySpeaker * lblSpeakerPrice.Text)
        If QtyComputer > 2 Then
            txtTotal.Text = Total * 90 / 100
        Else
            txtTotal.Text = Total
        End If

    End Sub
End Class

Buat case 3 tadi ya