Not directly in Google Earth, but with a few outside tools it is possible.
1) Save your placemarks/path as a KML file.
2)
here is a little online application that allows you to upload a KML and get back one with the absolute elevations of the points filled in for you.
3) Then there are various applications to plot profiles, I recommend
gpsvisualizer.com, if I remember the names of the others will post back. (you mentioned Excel, you might be able to open the KML from 2 in
GEpath, and copy the grid from there into Excel, and see what you can do with it there.)
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