Shipping Price calculation In Ratio

Dear All,

We have a business scenario in which we are capturing the shipping cost on material.

The process is as follow

Create PO-->>Inbound Delivery-->Shiping Document (VT01n)-->> Shipping Cost(VI01) -->>GRN.

The cost of shipping is calculated equally for each line item and loaded on material.Now business wants to Have this cost based on Value of material i.e dividing the amount based on ratio.

What will be the possible solution for this.

Have been looking for the solution but could not found any.

Thanks

Sachin.