Need help to write routine for create shipment

Dear All,

I have a requirement in the transaction VT01N at the time of creating shipment w.r.t the outbound delivery. Actually after enetring the distance in the stages tab I click on "Estimate freight cost" then system calculates the net value but this net value calculation doesn't involve the ship-to party criteria as ship-to party is not selected in the access sequence of condition record(VK11). I also searched the user exit through which can pass the ship to party in the condition record but to no avail. Now I have got some hint guy to try it out with Routine. Can anybody tell me how to go about it??

Thank you.

Anup.