Within a pivot table, how can I calculate a VARIANCE between 2 columns,
rather than the default "Grand Total" as shown below (i.e., I need to see a
variance of 8 on the Dog/Male row, rather than the "total" of 12) ?

Animal Gender Born Sold Grand Total
Dog Male 10 2 12
Female 5 2 7
Cat Male 1 1 2
Female 3 2 5
Hamster Male 6 3 9
Female 2 1 3