Procurement of transport

Hi Gurus,

We frequently take the help of a transporter for transportation.

For transporting from one city to another, we have fixed rate. example 100$ from A to B.

Currently, we purchase this service as follows :

We create a service master for this route, the service conditions and then service purchase order.

So when actual transportation happens, we create service entry sheet. In the place of quantity , we enter the number of trips made.The system calculates the price and posts the SES.( ie for 4 trips, in SES the amount is 4 x 100$= 400$)

But now we have another vendor, who has given us a two dimensional rate. i.e KM + weight.

i.e per km he has offered 2$ and for every 1kg he charges1$.

So if we have a cargo of 100kg for a distance of 10Km, then net payable is (100kgx1$) + (10Kmx2$)=120$

How can i map this in the service PO.

In the service entry sheet, how can i get the option of entering the weight as well as the kilometers

We do not have the transportation module.

Please help.

Thanks

Syed