How to control adding more custom object at design time

Sir I created a custom control collection. It invokes the collection editor dialog box with no propblem. Here i want to display a message box when we more number of objects (control) in the editor at design time. I want this messagebox to be displayed when the user clicks the Add button of collection editor. I found no where the method/event for collection editor Add button. Can you please give me some idea about this issue and how to arrive this with sample. Thanks in advance, arun

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