Thank you for all your reply. it work fine now. I hv follow up question , may i know how to make the line color as my wish , for example 2014 red and 2013 gray. of cos i can change to any other color i need in future.
Click on the + in front of the expression, choose BackgroundColor and enter as Definition =if(year=2014,red(), if(year=2013, lightgray())) or use lightred() for reds and for example rgb(150,150,150) for grays.