Adding asynchronous trigger for UpdatePanel to ImageButtons in Repeater in VB.NET

Sorry, I posted this in the wrong place (in the Web Forms section). I'd appreciate it if a moderator would delete the other thread.

OK, I've got a literal in an UpdatePanel, nd a repeater outside the UpdatePanel with among other things an ImageButton named btnBuy in the ItemTemplate.W hat I want to do if possible is to trigger a refresh of the UpdatePanel from the repeated ImageButtons in the Repeater ContentTemplate.

Below are the relevant bits -

Private Sub rpt2_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs)

End Sub

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Literal ID="BasketLiteral" runat="server"></asp:Literal>
</ContentTemplate>
</asp:UpdatePanel>

<asp:Repeater ID="rpt2" runat="server" OnItemDataBound="rpt2_ItemDataBound">

<ItemTemplate>
'''''other content of ItemTemplate
<asp:ImageButton ID="btnBuy" visible='<%#EvalEnabled(Eval("Stock").Tostring()) %>' ImageUrl="/Resources/images/buy.jpg" runat="server" />
'''''other content of ItemTemplate
</ItemTemplate>
</asp:Repeater>

I'd appreciate any help with this.

Thanks in advance.