Requestor name change through i Procurement form

We are on R12 and trying to implement iProcurement using smart forms. When I go to the smart form and enter the details and checkout I land up on the 'Checkout: Requisition Information' page where I have a field called 'Requestor' and is defaulted by my name. I want to change it to another person, however, I am not able to do that as there is only my name in the list of value. I want my name to appear as preparer but requestor name I want to select.

Thanks