I'm trying to set-up a register observation that emails whenever a planned delivery date has changed.

I have tried various different settings, but it never works quite how I want it.


The closest I've gotten is this:

Line 1: Type: Watch Field : PlanShipDate
Line 2: Type: Equals Field: OrderType Parameter 1: Normal

This works but it emails whenever an order planned delivery date has been entered (i.e. from no planned delivery date to 23/04/2019)

I want it to only email when a planned delivery date has been changed. Is this possible?