Dax Measure of LAST DISCOUNT Amount

[shophoney]

Hello all, I am in desperate need of some help with rolling back our inventory and seeing what the discount amount was on a prior date.

I have a measure that rolls back the date and I have a table with the historical discounts by date.

What I need to see is:

SKU QTY DISCOUNT AMOUNT VALUE

This measure shows me -8 (meaning 8 days ago)
ROLLBACK DAYS:=SUM ( ConfigurationTable[ROLLBACK #DAYS ])

This measure shows me the last discount date. But Items have been discounted many times. So what I need to see is the discount amount 8 days ago.
LAST DISCOUNT DATE:=MAX(tblInvPriceDisc[start_active_dt])

I think it might require the EARLIER function?

Thanks