I'm not sure if I recreated your setup, but maybe this can give an idea.
You could try a calculated field like:
IFNULL( SUM( [Value] ), LOOKUP ( SUM ( [Value] ), -1 ) )
In your calculated field, is your [Retail Price] an aggregate
and [Sales Date] is not? If so, you should be able to aggregate
[Sales Date] with an ATTR or maybe a MAX or MIN.
Please see workbook v10.3 attached in the Forum Thread:
289448null.twbx 17.5 KB