Is it possible to create a second y-scale (say on the right hand side), that is a computed, alternate version of the regular y-axis on the left hand side?

I wish to show both an absolute number (on the left) and a % change, on the right. This is for a financial time series.

For performance reasons, I'm opting for "calculated" here, as in , I'd prefer not to double the data for the y values... is there perhaps some sort of callback that I could supply, that would then be able to return the equivalent % value for the alternate y-axis?

Appreciate any pointers!

Many thanks.