Series.BubbleSizes (Word)

Returns or sets a string that refers to the worksheet cells that contain the x-value, y-value, and size data for the bubble chart.

When you return the cell reference, it will return a string that describes the cells in A1-style notation. To set the size data for the bubble chart, you must use R1C1-style notation.

With ActiveDocument.InlineShapes(1) 
 If .HasChart Then 
 MsgBox .Chart.SeriesCollection(1).BubbleSizes 
 End If 
End With