load data to user control

hi friends i am using vs2005.
 
i have ceated a user control.
 
i am using this user control.
 in my aspx file, i have a ajax tab container.
My requirement is on clicking a button the user control should be added to the tab dynamically. This works fine but when i try to bind the data to the controls in the user control from the aspx page, it is giving "object reference not set to null error"
 
my button click event is
 private void AddPanel()
 {
  TabPanel tp = new TabPanel();
        tp.HeaderText = "Processing Step " + i.ToString();
       
        Control c = LoadControl("DynamicTabUserControl.ascx");
        ListBox lb = (ListBox)c.FindControl("SpecialGroupList1");
  &n ...