Calculate Norm Dist using pivot table

Hi all,
I am looking to create a monthly report containing normal distribution graph using a pivot table. Its important to use pivot tables as the data keeps changing month-to-month. I was able to create Column containing Average, StDev as they are calculated fields provided by Excel. However, I need to create another column which will contain norm.dist(row_item, grandtotal mean, grandtotal stDev). You can create custom formula in pivot tables however you need to insert the original fields. But this formula requires the grandtotal values.

Any ideas on how I can achieve that will be helpful! Thanks soo much! report is attached