how to disable or restrict PO Header DFF in RFQ form

Hi, we use the DFF PO Header (in PO form) to save extra information for purchase orders. One of the segment of the DFF is mandatory.

The problem is that the same DFF is visible at RFQ form and every time we create an RFQ we have to complete the flexfield even when there is no PO information.

How can I disable or avoid to complete the DFF when creating the RFQ?

Thanks.