I have a line chart with three series over time. One series represents
actual values. For future dates, I made a formula return "#N/A" so
that they won't be plotted.

For one of the other lines, I would like to do something similar for
*past* dates up to March 2008. When I change the source data to start
at the March 2008 value, of course this skews the graph and puts the
March 2008 value where the graph starts, at November 2007. I can't do
the #N/A trick, since other data depends on these values.

I would be happy to just right-click and hide the November through
March data points manually. However, the three data series overlap at
many places, and it's impossible to just pick out the ones I want.

Any suggestions?

Thanks,
Rachel