How can I flag groups of workers as ineligible within a compensation plan, but exclude others?

One of our compensation plans includes workers based on an eligibility profile on their Person Type & Assignment Category. Within this group of eligible workers, we'd like a subset of these worker records to be read only i.e., to be included in the plan, but as non-editable.

This subset of workers can be identified by a specific value in their Employment - Job Attribute 1 field. I've tried selecting the 'track ineligible workers' in the Plan Eligibility screen, but then all ineligible workers are displayed in the plan as read only, not just those with the Job Attribute 1.

Does anyone know how to include a subset of workers in a plan as ineligible, but have another group of ineligible workers excluded from the plan?