I don't think this is possible in LV6.1. Probably the best thing you can do is work around it by dividing one dataset by a suitable number and then making the scale on the right side yourself. This is easy if you have a fixed Y scaling. If you have automatic Y scaling, this can be "followed" automatically by calculating from the YScale.Increment property, moving string indicators around programatically etc., but it will be a lot of work.
Martin