Private Sub btnOk_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOk.Click
        'Calculate Yacht Charges based on rates

        Dim intIndex As Integer = 0
        Dim intHrsCharted As Integer
        Dim decPrice As Decimal
        Dim decItemAmount As Decimal
        Dim strMessage As String

        Do While intIndex < lstYachtSize.Items.Count
            If lstYachtSize.SelectedItem(0) And cboYachtType.SelectedItem(0) Then
                decPrice = mdecSize22_RATE
            ElseIf lstYachtSize.SelectedItem(1) And cboYachtType.SelectedItem(1) Then
                decPrice = mdecSize24_RATE
            ElseIf lstYachtSize.SelectedItem(2) And cboYachtType.SelectedItem(2) Then
                decPrice = mdecSize30_RATE
            ElseIf lstYachtSize.SelectedItem(3) And cboYachtType.SelectedItem(3) Then
                decPrice = mdecSize32_RATE
            ElseIf lstYachtSize.SelectedItem(4) And cboYachtType.SelectedItem(4) Then
                decPrice = mdecSize36_RATE
            ElseIf lstYachtSize.SelectedItem(5) And cboYachtType.SelectedItem(5) Then
                decPrice = mdecSize38_RATE
            ElseIf lstYachtSize.SelectedItem(6) And cboYachtType.SelectedItem(6) Then
                decPrice = mdecSize45_RATE
            Else
                MessageBox.Show("Item is not in the list", "No item match", _
                MessageBoxButtons.OK, MessageBoxIcon.Information)
            End If

            'Calculate extended price and add to order total

            If txtHrsCharted.Text <> "" Then        'Not blank
                If IsNumeric(txtHrsCharted.Text) Then   'Is numeric
                    Try
                        intHrsCharted = CInt(txtHrsCharted.Text)
                        decItemAmount = decPrice * intHrsCharted
                        mdecTotal += decItemAmount
                        lblTotalCharges.Text = FormatCurrency(decItemAmount)
                    Catch ex As Exception
                        strMessage = "Calculation error."
                        MessageBox.Show(strMessage, "Error", _
                         MessageBoxButtons.OK, MessageBoxIcon.Error)
                    End Try
                Else                'Missing data
                    strMessage = "Enter the quantity."
                    MessageBox.Show(strMessage, "Data entry erro", _
                     MessageBoxButtons.OK, MessageBoxIcon.Information)
                End If
            End If
        Loop
    End Sub