Question: I have a Pivot table in excel that is using a raw table as its data source. This pivot table is doing a bunch of grouping and summing of rows. 

I'd like to now use the result of this new pivot table as the data source for a new pivot table which will further modify this data. 

Is this possible with excel? I suppose you could call it 'nested pivot tables'

Answer: 
* Make your first pivot table.
* Select the first top left cell.
* Create a range name using offset:

`OFFSET(Sheet1!$A$3,0,0,COUNTA(Sheet1!$A:$A)-1,COUNTA(Sheet1!$3:$3))`
* Make your second pivot with your range name as source of data using F3.

If you change number of rows or columns from your first pivot, your second pivot will be update after refreshing pivot

GFGDT
As @nutsch implies, Excel won't do what you need directly, so you have to copy your data from the pivot table to somewhere else first. Rather than using copy and then paste values, however, a better way for many purposes is to create some hidden columns or a whole hidden sheet that copies values using simple formulae. The copy-paste approach isn't very useful when the original pivot table gets refreshed.

For instance, if Sheet1 contains the original pivot table, then:

* Create Sheet2 and put `=Sheet1!A1` into Sheet2!A1
* Copy that formula around as many cells in Sheet2 as required to match the size of the original pivot table.
* Assuming that the original pivot table could change size whenever it is refreshed, you could copy the formula in Sheet2 to cover the whole of the potential area the original pivot table could ever take. That will put lots of zeros in cells where the original cells are currently empty, but you could avoid that by using the formula `=IF(Sheet1!A1="","",Sheet1!A1)` instead.
* Create your new pivot table based on a range within Sheet2, then hide Sheet2.