DisplayRSquared Property [Excel 2003 VBA Language Reference]
True if the R-squared value of the trendline is displayed on the chart (in the same data label as the equation). Setting this property to True automatically turns on data labels. Read/write Boolean.
This example displays the R-squared value and equation for trendline one in Chart1. The example should be run on a 2-D column chart that has a trendline for the first series.
With Charts("Chart1").SeriesCollection(1).Trendlines(1) .DisplayRSquared = True .DisplayEquation = True End With