Updating MSGraph datasheet in Word from VB

[blurbology]

I have a word document that contains a Graph (MSGraph). I am trying to update the Chart's datasheet with new values, but I cannot seem to get the correct reference for the chart object. What I am trying is:

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Dim oShape As Microsoft.Office.Interop.Word.Shape
Dim oGraphChart As Microsoft.Office.Interop.Graph.Chart

word = CreateObject("Word.Application")
word.visible = True
doc = word.Documents.Open(My.Settings.FormsPath & "\49.doc")

oShape = doc.Shapes(1).OLEFormat.Object
oGraphChart = oShape.OLEFormat.Object

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I am gettig a NullReferenceException(Object reference not set to an instance of an object) at:

oShape = doc.Shapes(1).OLEFormat.Object

however, if I do not have an exisiting chart, and simply add a new one using:

oShape = doc.Shapes.AddOLEObject(Left:=40, Top:=400, Width:=400, Height:=400, ClassType:="MSGraph.Chart", DisplayAsIcon:=False)

then this provides a reference to the chart object that I can use.

Any suggestions?