I'd like to add data labels to some of the data points on a line chart.

I know how to do it manually, but I'd like to do it in a way that
permanently associates the data label with the data point in the underlying
data series.

For example, I might have a graph of stock prices, which would show jumps or
drops at certain points. I might want to label one point with "Yahoo rejects
Microsoft offer" and another with "Apple introduces iPhone".

I'm using Excel 2003.

Thanks.