Shopping Cart does read textbox value from gridview

I have a gridview with a selection of databound items as well as a textbox and a button, the purpose of the textbox is to allow the user to enter the quantity required and then click on the button which will save the data and show the shopping cart. The textbox is in a itemtemplate tag, and the client doesn't want to select the row (ie edit mode) then add the value.

The problem is I can't get access to the textbox value I either get no value or an "object reference not found error" Surely there is some way of doing this? I have tried various methods ie :-
Dim tmpqty As TextBox = Me.GridView1.SelectedRow.Cells(4).Controls(0)
Dim tmpqty As TextBox = CType(Me.GridView1.FindControl("TextBox1"), TextBox)
etc
in various events BUT NOTHING WORKS HELP!!!

Imports System.Data.SqlClient
Imports System.Data
Partial Public Class OnDemandLine
    Inherits System.Web.UI.Page
 
    Public cnstring As String
 
    Private Sub OnDemandLine_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
 
    End Sub
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Select Case Request.Item("t")
            Case "ond"
                CType(Me.Master.FindControl("lblPageTitle"), Label).Text = "On Demand Product Lines"
                ViewState("type") = 3
            Case "bwrk"
                CType(Me.Master.FindControl("lblPageTitle"), Label).Text = "Bespoke Workbooks"
                ViewState("type") = 4
            Case "std", "pblc"
                Response.Redirect("standardproductline.aspx?t=" & Request.Item("t"))
            Case Else
                Response.Redirect("standardproductline.aspx?t=" & Request.Item("t"))
 
        End Select
 
        cnstring = ConfigurationManager.ConnectionStrings("Rogensi").ConnectionString
        If Not Me.IsPostBack Then
 
            binddata()
        End If
 
    End Sub
 
    Sub binddata()
        Dim cmd As Data.SqlClient.SqlCommand
        Dim da As New Data.SqlClient.SqlDataAdapter
        Dim ds As New DataSet
        Dim cn As New Data.SqlClient.SqlConnection
        cn.ConnectionString = cnstring
 
        cmd = New Data.SqlClient.SqlCommand
        cmd.CommandText = "showproductline"
        cmd.CommandType = CommandType.StoredProcedure
        cmd.Connection = cn
 
        Dim pagep As New SqlParameter("@type", ViewState("type")) 'ViewState("id")) '
        cmd.Parameters.Add(pagep)
 
        da.SelectCommand = cmd
        da.Fill(ds)
 
        Me.GridView1.DataSource = ds.Tables(0)
        Me.GridView1.DataBind()
 
 
        da.Dispose()
        cmd.Dispose()
        cn.Close()
    End Sub
 
--------------ASPX page---------------
<%@ Page Language="vb" AutoEventWireup="false" MasterPageFile="~/RogenSi/Site1.Master" CodeBehind="OnDemandLine.aspx.vb" Inherits="RogenSi.OnDemandLine" 
    title="On Product Line" %>
<%@ MasterType VirtualPath="~/RogenSi/Site1.Master" %>
 
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" BorderStyle="None" GridLines="None" HorizontalAlign="Left" DataKeyNames="id">
        <Columns>
            <asp:ImageField DataAlternateTextField="title" DataImageUrlField="image" DataImageUrlFormatString="~/siteimages/{0}" HeaderText="Item">
                <ItemStyle Height="50px" Width="50px" />
            </asp:ImageField>
            <asp:TemplateField HeaderText="Short Description" SortExpression="SDescription">
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("Title") %>'></asp:Label><br />
                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("SDescription") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField DataField="UnitPrice" HeaderText="Unit Price" SortExpression="UnitPrice" />
            <asp:BoundField DataField="StockLevel" HeaderText="Stock Qty" SortExpression="StockLevel" />
            <asp:TemplateField HeaderText="Order Qty">
                <ItemTemplate>
                    <asp:TextBox ID="TextBox1" runat="server" Width="50px"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:ButtonField ButtonType="Button" CommandName="select" Text="ADD" />
            <asp:BoundField DataField="LeadTime" HeaderText="LeadTime" SortExpression="LeadTime" Visible="False" />
            <asp:BoundField DataField="id" HeaderText="id" InsertVisible="False" ReadOnly="True"
                SortExpression="id" Visible="False" />
            <asp:BoundField DataField="ProductType" HeaderText="ProductType" SortExpression="ProductType"
                Visible="False" />
            <asp:BoundField DataField="ReStockLevel" HeaderText="ReStockLevel" SortExpression="ReStockLevel" Visible="False" />
        </Columns>
        <EmptyDataTemplate>
            Sorry there is no data for this category
        </EmptyDataTemplate>
    </asp:GridView><br />
    <asp:Label ID="Label3" runat="server" Text="Label4"></asp:Label>
 
</asp:Content>

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