Check to ensure purchase order line has an approved requisition (either online or paper attached)

Hi members,

I am trying to solution for a requirement which goes this way.

Requirement : Our company uses both online requisitions and paper requisitions. Online requisitions, once approved, make it as purchase order lines through Autocreate. For those manually added, a check should be enforced to see if an approved paper requisition is attached.

Solution I am thinking of: On the purchase order form, I have a personalization to check if the line is sourced from requisition
          1) In the distribution, requisition number is present and is from an approved requisition OR

          2) (A requisition printed on paper requisition is entered  AND Approved paper requisition is attached