yes, I use office 2010 and office 2007 should be same.
When you single click on PT, you will get Pivottable Tools and Options and Design tab highlighted, in options tab you will see refresh and change data source under Data frame and clear, select, and move pt under Actions frame, like wise next to it you have calculations frame.
It is just above "Field, items and sets" where you click for adding field.
Unfortunately, I dont know what the correct names for these tabs/frames/toolbar/ribbons, and I dont have option to give you screenshot.
I am sorry if I am confusing, the silver line is your problem has solution.
Regards,
Prasad DN