You need to add the customer segment to your customer record type with data sync...

Whenever you create a new record in your process model, you calculate the customer segment in a Script-Task and update the record before storing it.

Add a custom record field to the customer record type that evaluates the three given attributes to define the customer segment.

You add a new combined record field, link it with the business rule (expression rule), and define the update frequency on the combined field.