Requirement of Supplier and Supplier Site field mandatory while creating Purchase Requisition

Summary: When Creating Requisition through Noncatalog Item Request page for a specific BU the Supplier and Supplier Site Field are presently Non Mandatory.Once the Supplier is entered,then the Supplier Site field becomes mandatory.The only requirement is to make the Supplier field mandatory and keep the Supplier Site field mandatory after the Supplier has been entered.Can you please let us know whether this can be achieved through Sandbox personalization or any other process/functionality?The same requirement is for Requisition created throgh a smart form also.This is a BU specific requirement

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