PIVOT Calculated Field %

[RattlingCarp3048]

This is a snapshot of my pivot table. I need to make a calculated field that shows the % of cases that did meet TAT. How do i convert this formula into one the PIVOT will recognize/accept? is it even possible?

(Count of Meet TAT = Yes ) / Count of Accession #

in this example the name "Emmons" had 6 Accessions total and only 4 Met the TAT so (4 / 6= 67%)

Row Labels	Count of Accession #	Count of Meet TAT?
Consult	1322	1322
- AMP	31	31
- Emmons	6	6
- No	2	2
- Yes	4	4