This is a much neater way than I found which was to use the full name of the Panel with all the containers it was contained within.  ie.  MainContent_ContentPage_DetailsPanel_TabContainer1_Tab1_Panel1    etc... 
  
  
Thanks for you help.  Everytime I click on the bar I enjoy the way the second chart now updates! 
  
  
  
Cheers 
  
  
  
Martin