Error: .attachEvent is not a function

[tom]

I have a delete button on my toolbar that I need a popup before deleting.

So, I need the delete button on the toolbar to confirm the user really wants to.

I've followed the instructions below:
http://www.telerik.com/help/aspnet/toolbar/tool_stop_postback.html

I get the following error in my Firefox error console:  "....attachEvent is not a function"

Here is my radtoolbar:

<telerik:RadToolBar ID="UserAccessEditToolBar" runat="server"/>

and here is my javascript:

<script type="text/javascript">

<%= UserAccessEditToolBar.ClientID %>.attachEvent("OnClientClick","click_handler");

function click_handler(sender, e)
{
   if (sender.CommandName == "clientside")
   {
       // call clientside function here
       return false;
   }
}

</script>

any suggestions?

[tom]

Resolved
we found this article:
http://www.telerik.com/support/kb/aspnet-ajax/window/using-radprompt-and-radconfirm-with-telerik-navigational-controls.aspx

which gave us the javascript below

<script type="text/javascript">
        var lastClickedItem = null;
        var clickCalledAfterRadprompt = false;
        var clickCalledAfterRadconfirm = false;
        function toolbarClicked(sender, args)
        {
            if (args.get_item().get_text() == "Delete")
            {
                if (!clickCalledAfterRadconfirm)
                {
                    args.set_cancel(true);
                    lastClickedItem = args.get_item();
                    radconfirm("Are you sure you want to postback?", confirmCallbackFunction);
                 }
            }

        }
         function confirmCallbackFunction(args)
        {
            if (args)
            {
                clickCalledAfterRadconfirm = true;
                lastClickedItem.click();
            }
            else
            clickCalledAfterRadconfirm = false;
            lastClickedItem = null;
        }
        </script>

then this was our toolbar line:

    <telerik:RadToolBar ID="UserAccessEditToolBar" runat="server" AutoPostBack="true" OnButtonClick="UserAccessEditToolBar_ButtonClick" OnClientButtonClicking="toolbarClicked" />

OnClientButtonClicking fires the javascript and the confirmation box.

If the user hits OK and wants to delete the item, then the "OnButtonClick" is fired and actually deletes the record.