Have you tried making the changes you want to the chart whilst in Macro record and then viewing the code produced. This gives you all the properties and methods you need for the action you are after which can then easily (?) be converted to LabVIEW. I have used this strategy in the past when getting LabVIEW to do things to Excel with varying degrees of success.
OK It's been some time but I just found the way to do this while working on something else. See solution in the attached vi (you will have to adjust the limits).
