Change color of single horizontal (x) axis line?

[bondjel]

I have a chart where a single horizontal (x) axis line has special importance. Is there a way to change the color of just that single horizontal line? I know I can change the color of ALL of the x axis lines but that is not what I want to do. Thanks in advance.

[Andy Pope]

If by axis line you mean gridline then no you can not format individual ones.
The normal work around is to use a dummy series. But the major problem is the line may appear above the other chart elements rather than behind.