Fixed Condition record issue

Dear All,

I have maintained a Header condition record which is for fixed amount  and iam doing a partial billing for it now my requirment is even in partial billing system has to show what ever fixed amount condition record i have maintained in sales order.

For Example

Header condition is 20 and quantity 10 in sales order and in  billing quantity is  8, 4 in 1st line item and 4 in second line item.

So as per my requirement it should be like below.

Sales Order                       billing

item 1   Pr00 100                 item 1  pr00 100

             Zk01   10                            zk01 10

item 2 Pr00 100                   item 2 pr00 100

           zk01  10                               zk01 10

regards,

udai