Update Panel not updating in Lightbox

I have a repeater of photos and they open in Lightbox when clicked on each photo. There is a description at the bottom of each photo. What I want to do is to be able to have an update panel within this lightbox, so that people can edit description of each photo.
<asp:Repeater ID="rptPhotos" runat="server" OnItemDataBound="rptPhotos_OnItemDataBound"> <ItemTemplate> <img src="Library/test1.jpg" /> <asp:UpdatePanel ID="udpPhoto" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:Label ID="lbDescription" runat="server"></asp:Label> <asp:LinkButton ID="btnEdit" runat="server" Text="Edit" OnClick="btnEdit_onClick"></asp:LinkButton> <asp:TextBox ID="txbDescription" runat="server" Visible="false" CssClass="editable"></asp:TextBox> <asp:Button ID="btnSave" runat="server" Text="Save" Visible="false" /> ...