Control with collection property that is editable control in desig

[Sean]

Hello,
I want to implement a control that has collection property and it's content
is editable in designer in ASP.NET v2.0
The example would be :
<CustomControls:TabbedControl>
<CustomControls:Tab><!-- can drag and drop controls in
designer--></CustomControls:Tab>
<CustomControls:Tab><!-- can drag and drop controls in
designer--></CustomControls:Tab>
</CustomControls:TabbedControl>

I've been looking on the web, and didn't find a clue to how to implement
this sort of control. Working with ASP.NET2 I've managed to get
ContainerControlDesigner, but only for a stand alone control.

Thank you,
Sean