I'm not sure, but I think it can be done with Window_Avg.
I didn't have access to your data, so I typed in some of the values
and validated what I thought was the wt. avg against excel.
I may have guessed wrong on how you calculated it.
SUM([wt (286680avg)].[variance %])*SUM([Out Count])/(TOTAL(SUM([Out Count])))
Daily average of wt avg:
For the chart, because [Product] is needed for the calculations, [Product] needs to go on
the Detail shelf. This multiplies the copies of the correct value, so this can be reduced
by putting Index on the Filter shelf and filtering to 1.
The critical part is the table calculation setting shown below.
Please see workbook v10.1 and excel sheet attached in the Forum Thread: