Contingent Worker form and PO for temp labor

Hello,

I have a client with some contingent worker requirements and I am trying to test in a Vision instance (which could be the issue!), but I am just looking for a sanity check here.

If I create a supplier then a PO for temp labor and approve, shouldn't I then be allowed to place that approved PO number on the HR/Contingent Worker form?

The workers need to use iExpense but there is no place on the HR form to enter a cost center so I assume the only way is to link the PO to the HR form. Am I crazy or is there another way to add a cost center to the HR Contingent Worker form?