Using a class to dynamically load user controls

Question

I am makign extensive use of user controls. I am dynamically populating them. My plan was to use a single class to decide which controls should be loaded into place holders on a given page. This class would then passback each control. The page itself would only load the control. However, i can't seem to access my user controls from classes. I also can't figure a way to import the ASP namespace. Any ideas?