Hi Alan,
Here is one way, there are others:
1. Select the series on the chart, not the legend. Note that there is a
formula on the Formula Bar that looks like:
=SERIES("series1",A1:A10,B1:B10,1) or
=SERIES(,A1:A10,B1:B10,1)
Of course your formula has different references including the sheet names.
The first argument of the series function is the series name, it is what the
legend uses. Enter a name after the "(" and before the first ",". Enter the
name you want to use putting quotes around it like in the first example
above. Or refer to a cell:
=SERIES(C1,A1:A10,B1:B10,1) where C1 has the name you want to use.