landed cost in shipment document to be copied into purchase order

Dears,

i need to create conditions in shipment cost to be copied into purchase order before GRN as the following example:

Purchase order conditions ZFR1 , ZFR2 , ZFR3

shipment cost conditions will be the same.

i need to enter the exact amount in the shipment cost then it will be copied to each condition

can you provide step by step to solve that case.