Show dependendent values on pie chart

I was trying to use the solution from the link

When using the the solution LabeledPieChart from the answer to this question, I get the error "The property customControls:LabeledPieChart.Series is not declared as an attachable property". I am using silverlight 4 and the caliburn framework. I have though downloaded the source code that is provided in silverlight 3 and able to run it succesfully in silverlight 4. Could you please help on this? Help required ASAP