help with datagrid

[smd5049]

I have a datagrid bound to a sql proc. I have made the last column in the datagrid into text boxes so the items are editable. how do i return the values from these cells? Basically I want to be able to sum the entire column, as well as set the values in each item of the column to 0 upon a button_click. I'm very new to vb.net and if I'm not explaining this correctly please let me know.

the datagrid is built through this funtion:

Dim strConnString As String
            Dim strSQLText As String
            strConnString = ConfigurationManager.ConnectionStrings("SDWConnectionString").ToString
            strSQLText = "SELECT TN_CN_S_Desc, Item, Pack, Location, Lot, Label_Nb from sdw.sdw_user.SAR_DTD_840_copy where Pick_Num = '" & Picklist & "'"

            Dim SqlCOnnection As New SqlConnection(strConnString)
            SqlCOnnection.Open()

            Dim sqlCmd As New SqlCommand(strSQLText, SqlCOnnection)

                     Dim adapter As New SqlClient.SqlDataAdapter(strSQLText, SqlCOnnection)

            Dim ds As New DataSet
         
            adapter.Fill(ds, "sdw.sdw_user.SAR_DTD_840_copy")
            Dim dataTable = ds.Tables("sdw.sdw_user.SAR_DTD_840_copy")

            Me.DataGrid1.DataSource = dataTable
            Me.DataGrid1.AutoGenerateColumns = False
            Me.DataGrid1.DataBind()

the html for the column that I made editable and want to sum/set to zero looks like this:

<asp:TemplateColumn HeaderText="# Labels">
                                        <EditItemTemplate>
                                            <asp:TextBox ID="txtlbls" runat="server" Style="text-align: right" Text='<%# DataBinder.Eval(Container.DataItem,"Label_Nb") %>'
                                                    Width="65"></asp:TextBox>
                                        </EditItemTemplate>
                                        <ItemTemplate>
                                            <asp:TextBox ID="txtlbls" runat="server" Style="text-align: right" Text='<%# DataBinder.Eval(Container.DataItem,"Label_Nb") %>'
                                                    Width="65"></asp:TextBox>
                                        </ItemTemplate>
                                    </asp:TemplateColumn>