Chart Data Expression Used in Reference Line

[Anonymous]

Hello,

I have a chart with the reasonably long expression of:

if( Mod( RowNo(),3 )=0, RangeMax(above(sum(A),0,3))-RangeMin(above(sum(A),0,3)))

Where A is my data field. The purpose of which is to create an S chart (moving range chart).

I want to use the data points for further calculation as a reference line but am unsure how this can be done. E.g Avg(expression), Stdev(expression).

Thanks for the help,

Joshua C