I am trying to change the color of one of the gridlines in my line chart (not
all of them). Since I have not seen any sort of formatting option along these
lines, I used the autoshapes function to simply add a colored line on top of
the desired gridline; however, I want to be able to update/add data for the
graph, and still have the colored line stay where its supposed to when the
graph changes. Is this possible?