Add Moving Range based on Axis.X as standard aggregation for Lines & Curves

Shewhart control charts for SPC generate upper and lower control limits based on the average 2 point moving range of the data.   Currently, the only ways to calculate these are through helper columns (which do not respond to data limiting), through document properties or scripting (hardcoded solution), or by using multiple Y axis variables with complex custom expressions.  

Having Moving Range based on Axis.X  ("MR([Y],2)" for 2-point moving range for example) available as a standard aggregation would allow UCL/LCL to be added as horizontal lines using Lines and Curves, greatly simplifying the ability to create Shewhart Control Charts on the fly.