Chart.DisplayBlanksAs (Word)

Returns or sets the way that blank cells are plotted on a chart. Can be one of the XlDisplayBlanksAs constants. Possible return values are xlInterpolated - Values are interpolated into the chart, xlNotPlotted - Blank cells are not plotted, xlZero - Blanks are plotted as zero.

With ActiveDocument.InlineShapes(1) 
 If .HasChart Then 
 .Chart.DisplayBlanksAs = xlNotPlotted 
 End If 
End With