You can leave the #N/A errors so they don't appear on your chart, and use
the following formula to calculate the maximum.

Assuming your data is in B1:B10,

=MAX(IF(ISNA(B1:B10),"",B1:B10))

entered as an array formula with Cntrl-Shift-Enter will give you the max of
your data even if it does contain #N'A error.

Dave

url:http://www.ureader.com/msg/10295975.aspx