amwkl4
AFIK: There is really no easy way to do this in excel for a "scatter chart" to create one you have to have a very-good to masters grasp if VBA to do anything of even a moderate complexity.
There is a YouTube video from LearnChemE (This poppedup in one of my searches on critical vales (triple-point :) )
YouTube-LearnChemE-3D Plots in Excel which shows how to use/create a surface chart. This may work for your needs.
There is however, a professor,
W. Kamakura (click for Bio), with Rice University that has developed an add-in and a worksheet that will help. He has however, encrypted and password protected these files.
Be advised we will not help anyone remove passwords nor encryption from such files.
In the Rice.edu personal pages you will find his offering (click thru the above link) or you can reach it directly here:
http://wak2.web.rice.edu/bio/WagnerK...aDownloads.htm
((This link was verified today 2015-10-24.17:00GMT)
Your only other option is to purchase some rather expensive add-in or software from a commercial site.
(I may update this post in a little bit... I haven't tried this in Excel2013 so there maybe something I've missed)