I have tried looking up for solution for my problem if it was already answered but could not find any such solution. The requirement is to trigger material determination ONLY when the ATP check fails (in other words when there is a stock shortage to confirm the order) for the material entered in the order. Some suggest Substitution reason 0004 but does not help as it triggers the substitution even when stock is available completely for the main item. Also, it does not propose the pop up for the user to select the substitute materials.
Any idea how to handle this with a requirement routine or enhancement would be appreciated.