Accessing DropShadow properties through javascript

I am have trouble accessing the properties of a drop shadow through javascript. My dropshadow looks like this

<asp:Panel runat="server" id="registeredusersTab"></asp:Panel>
<atlasToolkit:DropShadowExtender id="dsregisteredusersTab" runat="server">
<atlasToolkit:DropShadowProperties targetcontrolid="registeredusersTab" opacity="0" rounded="false" trackposition="true">
</atlasToolkit:DropShadowProperties
And I'm trying to use the following script on click of another link...
<script>
$object('dsregisteredusersTab').set_Opacity(0);
</script
Its basically can't find dsregisteredusersTab. Any help would be greatly appreciated...

You need an ID on the properties object itself, not the extender. Check out the DropShadow sample page for an example of this:

<asp:Panel runat="server" id="registeredusersTab"></asp:Panel>
<atlasToolkit:DropShadowExtender id="dsregisteredusersTab" runat="server">
<atlasToolkit:DropShadowProperties targetcontrolid="registeredusersTab" opacity="0" rounded="false" trackposition="true"ID="dsBehavior">
</atlasToolkit:DropShadowProperties>

...

<script>
$object('dsBehavior').set_Opacity(0);
</script>

Thanks