A sharepoint problem

I have a little problem.

the Excel web Access is work fine…

the only problem i have is when I add a subject in the Sharepoint List I cant see it Synchronize in the Excel web Access graph….
Excel services

But if I refresh threw the excel file…

in Data > refresh all ….it work.

How can I Synchronize the Excel web Access…soo after I will add a new subject the graph will show me the new details…?
witout going throew the excel file….