Supplementary billing for material dispatched from Depot to Customer

Dear All,

My client have a scenario where they had dispatched material to customer while negotiation is going on.

After price finalization, they will raise a supplementary bill to customer for material which had dispatched from the date from which new price got applied.

EX.-- New price got finalized on 25.01.2012 but applicable from 01.01.2012.

Now they will raise supplementary invoice for the material dispatched between 01.01.2012 to 25.01.2012.

I need process to map this scenario in SAP.

J1IS is not possible as it is specially created for plants as local number range is hard-coded in J1IS.

Please revert with valuable solutions.

Regards,

Balaji