DataTable; PostBack; Retain Added Rows

So I have a DataGrid, on the PostBack, i add some rows, then i click a button and the the Page_Load Sub runs, it identifies as "is Post_Back"....how do i retain/retrieve any previously entered rows on a post back? here is my code thus far:

VB Code:

<%@ Page Language="VB" %>
<%@ import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
 
<script runat="server">
 
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    
        If Not Page.IsPostBack Then
            
        Else
            Dim ds As New DataTable
            Dim dc1 As New DataColumn("ID", GetType(Integer))
            Dim dc2 As New DataColumn("Item", GetType(String))
            Dim dc3 As New DataColumn("ItemDescription", GetType(String))
            
            ds.Columns.Add(dc1)
            ds.Columns.Add(dc2)
            ds.Columns.Add(dc3)
        
            Dim dr As DataRow
        
            dr = ds.NewRow()
        
            dr("ID") = Rnd(3456)
            dr("Item") = "John Weidauer"
            dr("ItemDescription") = "One handsome devil"
            
            ds.Rows.Add(dr)
            
            DataGrid1.DataSource = ds
            DataGrid1.DataBind()
        End If
    End Sub
 
</script>

HTML Code:

<html xmlns="http://www.w3.org/1999/xhtml" >

<head runat="server">

    <title>Untitled Page</title>

</head>

<body>

    <form id="form1" runat="server">

    <div>

        <asp:DataGrid runat="server" id="DataGrid1"

                HeaderStyle-BackColor="LightGray"

                HeaderStyle-Font-Bold="True" />

        <br />

        <br />

        <asp:Button ID="Button1" runat="server" Text="Button" UseSubmitBehavior="False" /></div>

    </form>

</body>

</html>