Aggregated Oil Rate bbl/d as Calculated Variable in a Text Box

[Steve Ennis 2]

I have been searching and trying different expressions and I just can't get this correct. Basically I want to make a summary visiualization which will include Bbl/d as dynamic item in the text box. When I sum the Oil Rate I get the cumulative oil rate for all the wells in my group for all time (too large a number). I want the aggregation of theLast production rate for the wells in the grouping I have chosen.

This relative newbie would appreciate any help....Thanks