Enable project fields on the Expense Entry page when submitting on behalf of another employee?

The manager sets up his subordinate as a delegate so that the subordinate can submit expense reports on behalf of the manager. Both the manager and subordinate are assigned the Project Team Member role. When the subordinate submits an expense for himself, the project fields are displayed on the Create Item page. When the subordinate submits an expense on behalf of the manager, the project fields don't display. How can the project fields be editable when the subordinate submits an expense for the manager?