adding items to shopping card, problem with getting data from Radio button list

 Hi all,
I'm new on this forum and in programing/databased world so please be indulgent.
I'm trying to add an item to my shopping card where price depends on radio button list selected value. RadioButtonList calls dynamicly values from database. Under button click I have this code:
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Protected Sub ButtonBuy_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles ButtonBuy.Click
        Response.Write("Purchasing stock<br />")

        Dim CurrentProductID As Integer = Request.QueryString("ProductID")    'get the selected item from the QueryString
       
        If CurrentProductID = 0 Then CurrentProductID = 1 'this is the default item

  &n ...