David and Andy,
Thanks for your posts. Whether I use #N/A or =NA() I get the value 0 on my
chart and it is plotted so it looks like the value has gone down to zero. I
do not even want the line after November since we have not yet closed 12/2007.

The cell was originally formatted as a number and I tried number, general,
as well as text and nothing works. All return 0 and it is plotted with a line.

Thanks for your help.