I need to create a calculated field in a pivot table that would be the
ratio of two running totals already in my pivot table.  I would like
to avoid doing the calculation in cells outside the pivot table.

Here is how my data needs to look and I am unable to get the ratio
calculated:

Week   Running Total 1    Running Total 2            Ratio
1                2
3                            0.67
2                5                         10
0.50
3                7                         21
0.33
4               10                        40
0.25