[Help] Price calculations.

okay so i have to build a calculate button To calculate the amount due add the price of the accessories and the exterior finish to the base price and display the result in the subtotal control. Calculate the sales tax on the subtotal and display the result in the total control. Then subtract the trade in amount from the total and display the result in the amount due control.

This is My Current Code..If u guys could Take a Look at it Perhaps find any mistakes plz point them out...because its not working
[highlight=vb.net]
Public Class VBAutoCenter

'Declares Constant values that will never change
Const TAX_RATE_Decimal As Decimal = 0.08D
Const DETAILING_STANDARD_Decimal As Decimal = 1D
Const DETAILING_PEARLIZED_Decimal As Decimal = 345.72D
Const DETAILING_CUSTOMIZED_Decimal As Decimal = 599.9D
Const COMPUTER_NAVIGATION_Decimal As Decimal = 174123D
Const LEATHER_INTERIOR_Decimal As Decimal = 987.41D
Const STEREO_SYSTEM_Decimal As Decimal = 425.76D
Private Sub CalculateButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CalculateButton.Click

Dim CarSalesPriceDecimal, AccesoriesFinishDecimal, SubTotalDecimal, SaleTaxDecimal, TotalDecimal, TradeDecimal, AmountDecimal As Decimal
Dim ExteriorFinishDecimal As Decimal

If StereoCheckBox.Checked Then
AccesoriesFinishDecimal = STEREO_SYSTEM_Decimal
ElseIf LeatherCheckBox.Checked Then
AccesoriesFinishDecimal = LEATHER_INTERIOR_Decimal
ElseIf NavigationCheckBox.Checked Then
AccesoriesFinishDecimal = COMPUTER_NAVIGATION_Decimal
End If

If StandardRadioButton.Checked Then
ExteriorFinishDecimal = DETAILING_STANDARD_Decimal
ElseIf PearlizedRadioButton.Checked Then
ExteriorFinishDecimal = DETAILING_PEARLIZED_Decimal
ElseIf CustomizedRadioButton.Checked Then
ExteriorFinishDecimal = DETAILING_CUSTOMIZED_Decimal
End If

Try
CarSalesPriceDecimal = Decimal.Parse(CarPriceTextBox.Text)
Try
AccesoriesFinishDecimal = Decimal.Parse(AccesoriesFinishLabel.Text)
ExteriorFinishDecimal = Decimal.Parse(AccesoriesFinishLabel.Text)
SubTotalDecimal = CarSalesPriceDecimal + AccesoriesFinishDecimal
SaleTaxDecimal = TAX_RATE_Decimal * SubTotalDecimal
TotalDecimal = SubTotalDecimal + SaleTaxDecimal
Catch ex As Exception

End Try


CarPriceTextBox.Text = CarSalesPriceDecimal.ToString("C")
AccesoriesFinishLabel.Text = AccesoriesFinishDecimal.ToString("C")
TotalSubLabel.Text = SubTotalDecimal.ToString("C")
SaleTaxLabel.Text = SaleTaxDecimal.ToString("C")
TotalAmountLabel.Text = TotalDecimal.ToString("C")
TradeTextBox.Text = TradeDecimal.ToString("C")
AmountDisplayLabel.Text = AmountDecimal.ToString("C")

Catch ex As Exception

End Try
End Sub
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