condition type volume in MM

Dear All,

i want to make condition type based on volume data, which mains

i made PO order for two items material X & material Y

material X have volume 4 M3

material Y have volume 6 M3

the PO have fright on the header conditions 100 USD

i want to let material X take 40 USD from fright & Y take 60 USD from fright

at the end the fright is header condition will be distributed on the items based on the volume of the item

any ideas