Overlaid Control Charts

[#1]

I have a data set of 40 samples, each measured using two instruments.  I would like a single Individuals Control Chart with both variables on the same Y-axis.  But the Control Chart Builder only allows for a single Y variable.  I've tried overlaying both using scripts without success.

[#2]

I don't think you can get the overlaid effect in control chart builder. Have you tried plotting the control chart with Graph Builder? 

[#3]

Since control chart limits are for univariate situations where the control limits depend on the moving range (which is likely different for each Y), it would be incorrect to plot both on the same control chart. 

It is , OK to pilot both on at the same chart and graph builder will do that for you as Jarmo suggests.