Hi Juergen,
Thank you for confirming that this is only possible through BAdI.
I have another concern though, can we have a sequence inside the storage group. In case there are same batch and GR date in the stocks, we want to get the stocks from storage type 2 before storage type 1. I have checked internally in the table /SCWM/T301M that there's a sequence number, however it is never used during determination of source stocks.
Regards,
Tin