Conditions on RFQ Header are not changeable at PO Header level

Dear Gurus,

I have maintained a Quotation and enter the conditions on Header level in Quotation. Once i adopt the Quotation in Purchase Order, these conditions are displayed both at Item and Header level and i cannot edit the condition value at PO Header level, they are editable at Item level but not at header level.

I want to edit them at PO Header level too.

Please advise.

Johi Kapoor