How to add a button in Application Level Excel add-in?

I am creating an APPLICATION LEVEL Excel Add-in (using vsto 2500 SE, C#).
So I do not have access to the document-level classes? So I cannot do
this.Controls.Add(...) to dynamically add a button to a worksheet?

I am trying to let the user create a List in the excel 2003 worksheet, and
click my add-in action to create a button next to the list, and let the user
click on that button to take some action on that list. A generic handler
(C#) will handle the button click event, and linking of button to list would
be based on the name of the button and the list (any better way?).

How do I dynamically add a button to a worksheet when my code is an
application level excel add-in?

Thanks for you time.