Eliminating forecast on trendlines
 

Everytime I create a trendline in Excel 2000 the trendline is forecast about
ten additional data points to the right.
I do not want this (i.e., I don't want any forecast in the trendlines) but
when I go to the "format trendline" dialogue box and select options, the area
governing forecasting is greyed out.
If accessing this portion of the dialogue box is the way to eliminate the
forecasting of trendlines, how do I access it?

Thanks in advance,
--
Geoff