I have a chart using 2 different series where the values may vary greatly.

I would like to keep the scale matching on both the primary and secondary Axis regardless of the data in each, however the max value needs to be able to be flexible (ie I can't just set a static min / Max in the Format Axis option.)

I would like to use a cell to calculate the maximum of both sets of data, and then have the scale work off that cell.

I have not been able to find if this is possible. Any help would be greatly appreciated