Hi Yishih,
What do you mean by "automatically?" Yes, you can assign the label to a bar in VBA, if that is what you are asking. For example, the code
With activesheet.ChartObjects(1).Chart.SeriesCollection(1).points(4)
.hasdatalabel = true
.datalabel.text = "*"
End With
will turn on the datalabel for point 4 in series 1 of chart object 1 on the active worksheet, and set it to "*".
I hope this helps.
Damon