Process Flow - Only on first render of field and update of that field

Question

I have an object (Oppoortunity) that creates another object (Assessment) when the field "Assessment date and time" is updated. I only want the Object Assessment to be created once; the first time the "Assessmend date and time" field is updated.

I've added a checkbox "Has been edited" to the Opportunity object.

My process builder is as follows: When formula evaluates to true -

AND(ISCHANGED([Opportunity].Assessment_Date_and_Time__c),NOT([Opportunity].Has_Been_Edited__c))

Immediate Actions: Create and Assessment Record, and Update Has Been Edited Boolean to true.

This Process flow is not working; i.e. the "Has been edited" box does not select as true when the date'time field is edited.

What am I missing?

Answer 1

I did not have the formula evaluating each time the record was created or edited, but rather just when created. This was what was causing the issue.