Unable to update table based on value in telerik grid

hi,

I want to update table with the values in the column named Distribute on Date(see the screenshot) under telerik grid.  

screenshot (http://postimg.org/image/e0k3wjcnx/)

On button I want to run update query and then refresh the telerik grid.

I have used the following code :

ASPX:

<telerik:RadGrid ID="RadGrid_Date" ShowStatusBar="true" DataSourceID="Grid_Date_DataSource"
                                                        runat="server" AutoGenerateColumns="False" PageSize="10" AllowSorting="True"
                                                        AllowMultiRowSelection="False" AllowPaging="True" GridLines="None"><PagerStyle Mode="NextPrevAndNumeric"></PagerStyle><MasterTableView DataKeyNames="AdvanceTransPaymentFromCustomer_id" DataSourceID="Grid_Date_DataSource"><NoRecordsTemplate>
                                                                No records found.</NoRecordsTemplate><Columns><telerik:GridBoundColumn SortExpression="advance_id" HeaderText="Advance Id" HeaderButtonType="TextButton"
                                                                    DataField="advance_id" UniqueName="advance_id"></telerik:GridBoundColumn><telerik:GridBoundColumn SortExpression="Customer_id" HeaderText="Customer Id" HeaderButtonType="TextButton"
                                                                    DataField="Customer_id" UniqueName="Customer_id" /><telerik:GridBoundColumn SortExpression="trans_date" HeaderText="Transction Date"
                                                                    HeaderButtonType="TextButton" DataField="trans_date" UniqueName="trans_date" /><telerik:GridBoundColumn SortExpression="amount" HeaderText="Amount" HeaderButtonType="TextButton"
                                                                    DataField="amount" UniqueName="amount" /><telerik:GridBoundColumn SortExpression="trans_type" HeaderText="Transction Type"
                                                                    HeaderButtonType="TextButton" DataField="trans_type" UniqueName="trans_type" /><%--   <telerik:GridBoundColumn SortExpression="distribute_on_date" HeaderText="Distribute on Date"
                                                                    HeaderButtonType="TextButton" DataField="distribute_on_date" UniqueName="distribute_on_date"></telerik:GridBoundColumn>--%><telerik:GridTemplateColumn HeaderText="Distribute on Date" UniqueName="distribute_on_date"
                                                                    ShowFilterIcon="false" Groupable="false"><ItemTemplate><telerik:RadDatePicker ID="txt_distribute_date" runat="server" Skin="Simple" DateInput-Enabled="True"
                                                                            DbSelectedDate='<%# Eval("distribute_on_date") %>' onkeypress="return false;" /></ItemTemplate></telerik:GridTemplateColumn><telerik:GridBoundColumn SortExpression="advance_number" HeaderText="Advance Number"
                                                                    HeaderButtonType="TextButton" DataField="advance_number" UniqueName="advance_number" /><telerik:GridBoundColumn SortExpression="customer_number" HeaderText="Customer Number"
                                                                    HeaderButtonType="TextButton" DataField="customer_number" UniqueName="customer_number" /><telerik:GridBoundColumn SortExpression="business_name" HeaderText="Business Number"
                                                                    HeaderButtonType="TextButton" DataField="business_name" UniqueName="business_name" /><telerik:GridBoundColumn SortExpression="cust_name" HeaderText="Customer Name" HeaderButtonType="TextButton"
                                                                    DataField="cust_name" UniqueName="cust_name" /></Columns></MasterTableView></telerik:RadGrid>

Code Behind :

    Protected Sub img_button_send_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles img_button_send.Click
        If Page.IsValid Then
            Dim str As String
            For Each lsi As GridDataItem In RadGrid_Date.Items
                Dim date_pick As New RadDatePicker
                If date_pick.SelectedDate > DateTime.Today Then
                    str = "update tbl_AdvanceTransPaymentFromCustomer set distribute_on_date='" & CType(RadGrid_Date.FindControl(" txt_distribute_date"), RadDatePicker).SelectedDate & "' where AdvanceTransPaymentFromCustomer_id =" & lsi.GetDataKeyValue("AdvanceTransPaymentFromCustomer_id")
                    SqlHelper.ExecuteNonQuery(str)
                    Response.Write(str)
                    RadGrid_Date.Rebind()
                End If

            Next
            lbl_msg.Text = "Record updated successfully"
        End If
    End Sub

But this is not working as column named distribute_on_date does not get updated in table when date is changed in grid and update buttonDistribute on Date is clicked.