Hi Raymond,
I tend to use Global Attributes. Code in a Workflow Expression Robot as Greg Olson has shown above.
To display in the Details Tab, you'll want to go to the Type and Attribute Manager and Edit your Change Notice Type. Select the Layouts Tab and an appropriate Layout(s) see screenshot. From there you can drag and drop an Attribute into an existing Attribute Group or create a new Attribute Group. Note - Sub-Type Layouts inherit from parents.
BTW - Nice job on this PTC, Thanks! Having this type of capability to manipulate how information is presented to the User is really beneficial. Still room for improvement to streamline Administration.