Disabling ToolBoxItem in Vs ToolBox after some scanrio

[sarahh]

Hi,
I make a designer with Visual Studio 2010 and use also the Vs
ToolBox(adding custom controls) by the following:

IToolboxService toolBoxService =
(IToolboxService)Package.GetGlobalService(typeof(IToolboxService));
toolBoxService .AddToolboxItem(toolboxitem, category);
toolBoxService .Refresh();

After dropping specific toolboxitem control on the designer I need
that this item will be disabled (grayed out).

I have the following questions:
1. How could I disable toolboxitem, whereas other toolboxitem in it's
category remain enabled?
2. How I disable the dropping of this toolboxitem?

Thanks.