I'm not a Statistics person, so I don't know much about Frequency and Relative Frequency. But why do you want to have 2 axes on the same scale of a graph with different values? Do you need the axes to be on the same side like that, or would it work if one was on the left, and one on the right? Is your Y axis the value axis or category axis?
I don't mean to be a bother, just trying to help.