I am new to Excel 2003

I have a line chart for the year - Jan thru Dec. Right now the chart only
contains data for Jan thru April. Then the line goes down to the bottom of
the chart (to May - zero data point). I call this the "tail". I know it is
there because I do not have any data in May-Dec yet. But I want to get rid
of the tail. On Excel 2000, I was able to right click or left click (Never
could remember whether it was right or left) and choose "no line" and the
"tail" went away. Now when I do this, the tail jumps to the next month
(June). How do I get rid of the tail? I know I could limit the source data
to just the months I have data in, but I really do not want to go back into
the charts every month and re-set the source data each month. I have about
20 charts with anywhere from 2 - 6 lines on each chart. To do this would be
a real pain.

Can anyone help me or point me in the right direction? I need to complete
these charts today.

Aurora