Is it possible to write code for substitutes(alternate material) modifying standard MRP? Has someone done it? Where did you write the code? We want to keep it at MRP level as well as preserve it during planned order to process order conversion. We want to write custom logic in standard MRP so that substitutes can be taken care of by MRP. We also want the same logic for planned order to process order conversion . We are currently building the logic by storing reservations in one table and then influence MRP to read the data so that it will not create unnecessary receipts whenever substitute stock is available. Which place we should write our code in? Is it anyways possible?