NameIsAuto Property [Excel 2003 VBA Language Reference]
True if Microsoft Excel automatically determines the name of the trendline. Read/write Boolean.
Example
This example sets Microsoft Excel to automatically determine the name for trendline one in Chart1. The example should be run on a 2-D column chart that contains a single series with a trendline.
Charts("Chart1").SeriesCollection(1) _
.Trendlines(1).NameIsAuto = True
Applies to | Trendline Object