Contingent Working Functionality - PO setup in HR employee record

Hi,

As per my understanding about the Contingent Worker Functionality the PO needs to be specified in the employee assignment definition in HR.

Can I avoid doing that if:

1) Employee is defined as Contingent Worker in HR (without defining PO number)

2) PO is entered in Purchasing and Contingent Worked name is selected

Is the PO number automatically populated once the PO is approved?

Thanks,

cv