Consuming RSS feed in website

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C#

ASP.NET

Hello friends,

In my application i have used the RSS feed. i have used the following code

<div class="news-blog">
            <h4>
                News and events<div class="news_scroll">
                    <asp:LinkButton ID="btnDown" runat="server" onclick="btnDown_Click"></asp:LinkButton>

                    <asp:LinkButton ID="btnUp" runat="server" onclick="btnUp_Click"></asp:LinkButton>
                    </div>
            </h4>
            <asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="http://www.gatesfoundation.org/FileReturn.aspx?returntype=rss&feed=all"
                XPath="rss/channel/item [position()<=3]"></asp:XmlDataSource>

            <asp:DataList ID="DataList1" runat="server" DataSourceID="XmlDataSource1">
                <ItemTemplate>
                    <div class="news-events">

                        <table width="100%">
                            <tr>

                                <td>
                                    <div class="news-content">
                                        <h5>

                                    <asp:HyperLink ID="hypTitle" runat="server" Width="500px" Text='<%# XPath("title") %>'
                                        Target="_self" NavigateUrl='<%#XPath("link")%>'></asp:HyperLink>
                                </h5> </div><br />
                                <p>
                                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:Label ID="Label1" runat="server" Text='<%# XPath("description") %>'
                                        Style="float: right"></asp:Label>
                                </p>
                                </td>
                            </tr>

                        </table>
                        <br />
                    </div>
                </ItemTemplate>
            </asp:DataList>

from this i have shown the 3 news. but when i click on up button i want to the news from 2nd to 4th.in code behind i don't understand how can i change the positions of the news. i want just like XmlDataSource1.XPath = "rss/channel/item [position()<=3 && position()!=1]"; but it gives error. please help me.