formula help needed

Printed From: Crystal Reports Book — Forum Name: Technical Questions

My current formula doesn't take nulls or undocumented into account:
({PERINATAL_DELIVERY_MATERNAL.episiotomy}) <> "None"

How can I rewrite the formula to account for nulls?
in the formula editor flip the option to 'use default values for nulls'

NOT isnull({PERINATAL_DELIVERY_MATERNAL.episiotomy})
OR ({PERINATAL_DELIVERY_MATERNAL.episiotomy}) <> "None"