How would I set up auto sum in the Excel 2007 Quick Access bar?
 

I am trying to set up the auto sum button on the Excel 2007 quick access bar
similar to the way I had it set up on Excel 2003 spreadsheet. I see how a lot
of functions can be set up on the Excel 2007 quick access bar but not the
auto sum function.

How would I add the sum function to the quick access bar?