I had the same problem.
Change the 24's to suit you.

With cht.Plot.Axis(VtChAxisIdX) 'x axis
.ValueScale.MajorDivision = 1
.ValueScale.MinorDivision = 1
.CategoryScale.Auto = False
.CategoryScale.DivisionsPerLabel = 24
.CategoryScale.DivisionsPerTick = 24
End With