There is a 'chart' option in which you can specify options specifically for the chart component as opposed to the other components. The chart is a combo chart. In that option, you could possibly use the targetAxisIndex option for the series that you want to change, but I'm not sure even that will work. But if it does, then you'll have a few additional problems to overcome, mostly where the additional axis is displayed. Probably it would be easiest to target it at the '0' axis, which is on the left side, and to display it on the 'inside' of the chart area. Hope that helps.