When trying to control the embedded OLE object in the PP presentation, you need to use the Object property, then convert the variant to the proper Ref type (in this case MS.Graph.Chart). To access full control of the object, it is best to use the Application property. This will provide all of the properties of the embedded object. See the attached modified VI which demonstrates changing one point in the dataset.
Be sure to close all ActiveX references used in each VI.
Michael Munroe
Certified LabVIEW Developer
www.abcdefirm.com