How to plot differences between datatips like legend function

Hi,

I need to write the difference between two or four datatips on the plot like legend. Text function writes everytime as I zoom in.

Questions :

1) If marker one is the reference and if there is 4 markers, I need to calculate 3 distance w.r.t. marker one along x axis. 2) How to plot these mentioned 3 distances on the plot( by zooming into plot it will stay as legend ) on 3 different lines on a vertical allignment ?

WR