Need help to customize WIP backflush logic

Hi,

The requirement is to customize the WIP backflush Logic based on unique lot selection logic. In order to perform customization, we need some help to tell us where we could perform customization at Oracle Apps

The requirement from our client is that, They would like to tie the Lot number to one work order, Meaning a Lot number cannot be shared between work orders. This is because there will be multiple work orders running at the same time in production. This cause the problem for those common materials whereby system will backflush the same lot number for different work orders (If quantity is allow). But this is not the actual consumption in Production. Any suggestion on the solution?