The Value expression for the text box specifies a scope that is not valid for a nested aggregate.

I tried

=Sum(Code.Divide(sum(Fields!WeeklyUnits.Value),Sum(sum(Fields!EstUnits.Value)))
*
Sum((Code.Divide(sum(Fields!EstHours.Value)),Sum(sum(Fields!EstHours.Value,"Job")))))

And received a different error.

An unexpected error occurred while compiling expressions. Native compiler return value: ‘[BC30455] Argument not specified for parameter 'Denominator' of 'Public Function Divide(Numerator As Decimal, Denominator As Decimal) As Object'.’.