Hello MisterT,
you don't need VBA for that. What you DO need, though, is to calculate the percentages in your data table. Then, with the data labels on your chart, click on an individual data label, click into the Formula bar, enter a = sign and click the cell that has the percentage value you want to show. Repeat for all data labels.
For a large chart, this manual method may be a bit tiresome. Instead, you can use a free Add-in called XY Chart Labeler. It's available from here and can put labels on any kind of chart, not just XY.
see attached
cheers, teylyn