Actually, I found my answer in the thread below titled "some charts will not
show trendlines", dated 6/6/06. Thanks Andy!

http://www.microsoft.com/office/comm...xp=&sloc=en-us

"Chris Lawton" wrote:

I have a chart with two trendlines already showing, but when I try to add a
third trendline (for a third series), it won't show in the chart. It does
show in the Legend, but not in the chart.

Anyone have any idea what causes this?