http://www.telerik.com/support/kb/aspnet-ajax/splitter/dock-a-radslidingpane-on-expand.aspx
<
telerik:RadSplitter id="RadSplitter1" runat="server" height="708" width="100%" CssClass="Splitter.Forest.css" ResizeMode="EndPane" BorderStyle="None" Skin="Forest" EnableEmbeddedSkins="False" >
<telerik:RadPane id="Radpane1" runat="server" width="22" scrolling="None" minwidth="22" MaxHeight="708" >
<
telerik:RadSlidingZone id="SlidingZone1" runat="server" width="22px" clicktoopen="true" >
<telerik:RadSlidingPane id="MBOM" title="MBOM" runat="server" width="500px" MaxHeight="708" OnClientBeforeExpand="beforeExpand" >
<
script type="text/javascript">
function beforeExpand(sender,eventArgs)
{
var slidingZone = $find("<%= SlidingZone1.ClientID %>");
slidingZone.dockPane(sender.get_id());
eventArgs.set_cancel(
true);
alert(
"Your text in the alert function.");
}
</script>