First confirmed delivery date

Hello,

my customer has a requirement to keep trace of the first confirmed date at schedule line level: the order is first entered in the system, and ATP check gives a first confirmed date at schedule line level. If afterwards (due to production rescheduling or backorder or so on) the item/schedule line is rescheduled and the confirmed date is changed, we need to keep trace of the date originally confirmed, for performance measurement and to prioritize in case of new stock becomes available.

I found table VBEH (schedule line history) but seems not to be in use anymore, as there are no entries in it. Any idea on how to solve this?

Thanks