Determines a title for the main Horizontal Axis. Example:

Sub CommandButton1_Click()
  Set E3Chart1= Screen.Item("E3Chart1")
  Old = E3Chart1.HorAxisTitle
  MsgBox "Next"
  E3Chart1.HorAxisTitle = "!Test"
  MsgBox "Return"
  E3Chart1.HorAxisTitle = Old
End Sub