Using a simple workbook someone posted earlier today, I created two lines, with only one of the line's labels showing, using a formula like :
IF attr([Seller Name]) = "Seller 1" then AVG(Price) else null end
And placing it on the Text shelf. You may be able to adjust as needed for your scenario. Check out the tips at this site by Andy Cotgreave: Gravy Anecdote | Pouring stories about data onto the web.
Thanks... This looks like it could help, but I'm not sure how...
The example you shared has two lines that are extracted from the same measure, no? In the example I show in the second and third graphs, I have taken three measures and overlapped the graphs. I can't figure out from your example how to mark up just the "Sum(p)" line.