I am trying to figure out how to add high/low points to a line graph, similar to what sparklines have. The file I am using now doesn't allow me to add new columns of data, so I'm trying to figure something out that just updates dynamically using the data I already have in place.

This page has the thing I want to do, but it requires additional columns to be added to work, which I don't want:

http://excelmate.tumblr.com/post/259...n-a-line-chart

Any thoughts on how this can be done? I'd appreciate any help.