LFDAT in Product Allcoation

[sap_kiwi]

Product Allocation configuration allows you to select multiple dates e.g. delivery date LFDAT which it appears is part of the MCVBEP structure. How is this controlled? What field is passed from Sales Order/Schedule line to this as this field is not in VBEP?

We have a requirement to be able to use the Requested delivery date on the sales order for Product allocation and use a different material availability date for ATP. We tried using LFDAT in the configuraiton but how do you pass the value to this field?
LFDAT is typically on the delivery and not on the sales order although the structure MCVBEP implies it is the sales order schedule line. Is there an exit for this?

Thanks in advance