Pivot Table tools

I am playing around trying to familiarise myself with PivotTables in Excel 2002. I have found a lot of information on the intranet, but can find nothing relating to two of the icons on the PivotTables toolbar. These are "Include Hidden Items in Totals" and "Always Display Items".

No matter what I do, the "Include Hidden Items..." icon is always greyed out on my toolbar and clicking the "Always Display Items" icon appears to do absolutely nothing.

Can anyone help? Tell me what these do and and example of when they would be used / how to activate the icon?

Thanks