I am sure there is excel expert Here.

I just try to use VBA and it looks like do not work.
I can not find the way to seperate the TickLabels.

ActiveChart.Axes(xlCategory).Select

With Selection.TickLabels.Font
.Name = "Symbol"
.FontStyle = "Regular"
……
End With

What TickLabels Public Properties do you suggest to use to set ac_a and ac_b?