Matching annotation offset to plotted data

[amloosen]

I would like to set the height of an x-axis (range) annotation equal to the y-value of a plotted distribution at a specific but changing x-value (in the case of the picture at x=60). I thought this should be easy by using the offset function and computing the offset value as the difference between the max figure height and the y-value at this particular point on the x-axis. However, even though the max height of my entire figure is set to the max height of the plotted distribution, this does not seem to work. I assume this is because the offset might be defined in pixels.
Is there a way to match the units of the plotted data and the offset or do you have any other advice on how I could achieve this (drawing a line from the x-axis to the distribution)? Thanks in advance