No but you could add a dummy series as a straight line and format it to fit
your need
See http://www.andypope.info/charts/averageline.htm
best wishes
--
Bernard V Liengme
www.stfx.ca/people/bliengme
remove caps from email

"ejennings" wrote in message
...
Is there a way to make a single gridline bolder than the rest?