Is it possible to format *individual* gridlines?

[newaglish]

I would like to make the 0 line (X-axis) bold, to emphasise when my graphed
line drops below zero, but it seems as though I can only format all of the
gridlines together.

Is it possible to format a single gridline alone?

 

[Andy Pope]

Hi,

No you can not format individual gridlines.
To get the effect you can use a dummy series and format that.
See here for more information.

http://peltiertech.com/Excel/Charts/AddLine.html

Cheers
Andy