Hi Timothy,
The Coolite LoadMask property is used by internal logic only (you can set message and etc but you can't manage load mask (show/hide)). I can suggest next example
<script type="text/javascript">
function DoWork(panel){
var loadMask=new Ext.LoadMask(panel.body, {msg:'Working 5 sec...'});
loadMask.show();
//emulate 5 sec work
var task = new Ext.util.DelayedTask(function(){loadMask.hide();});
task.delay(5000);
}
</script>
<ext:Panel runat="server" ID="Panel1" Title="LoadMask processing example" Width="300" Height="150">
<Content>
Content
</Content>
<Buttons>
<ext:Button runat="server" ID="SomeWork" Text="Do work" AutoPostBack="false">
<Listeners>
<Click Handler="DoWork({Panel1});" />
</Listeners>
</ext:Button>
</Buttons>
</ext:Panel>
In this example I manually create load mask, show it and hide.
Please let me know if you need additional information.