How would I make this calculation in javascript

[lik34175419]

In Excel it would look like this: =(B31-B30)/B31

B31 Field is named: Yesterday's Plan

B30 Field is named: Yesterday's Actual

Simple percentage variance in excel however, not sure how to get this into My pdf table. I am using the most recent version of Acrobat DC.

Thank you in advance and sorry for the elementary question.

[try67]

A good place to learn about this subject: https://acrobatusers.com/tutorials/how-to-do-not-so-simple-form-calculations