I found the series function has Moving Average, or Exponential Average, but not Exponential Weighted Moving Average. Any idea of how to generate?

How to calculate LCL, CL, UCL? What I know is UCL and LCL are CL +/- sigma. However, I don't know how to calculate CL Say a XR2 chart has 2 plots - one is Average, and another for Range. Each of these plots has its own LCL, CL and UCL lines displayed on the plot. Average plot has its own value of LC...