You've probably noticed that Pivot Tables can be manipulated, using the data
from the last data refresh, even though the source data may have
subsequently been changed.  That's because Pivot Tables take a snapshot of
the data and store it in a hidden pivot cache. Consequently, each time you
base a pivot table on the same data, the workbook size increases by the size
of that data.

One way around that issue is to base the 1st Pivot Table on the source data,
then base all subsequent Pivot Tables (that would normaly use the same
source) on the original Pivot Table.

Here's how:
Selecting <data><pivot table> from the Excel Main Manu
Step_1: Select the data source.
Select this option: Another PivotTable report of PivotChart report.

You might think that the new Pivot Table would only use the visible data of
the referenced Pivot Table, but it doesn't. It means the new Pivot Table
will share the same pivot cache as the referenced Pivot Table, avoiding the
creation of a new pivot cache. Note: the new Pivot Table can view the data
differently from the original Pivot Table and is not restricted in its
analysis capabilities. Also, I'm pretty sure if you refresh any Pivot Table
using a shared pivot cache...ALL Pivot Tables sharing that pivot cache are
also refreshed.

Does that help?
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Regards,

Ron (XL2003, Win XP)
Microsoft MVP (Excel)