Here is some code to get you started:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim Shp As Shape, Rng As Range, Hght As Single, Wdth As Single
Hght = InchesToPoints(0.5): Wdth = InchesToPoints(2)
With ActiveDocument
Set Rng = Selection.Range.Characters.First
Set Shp = .Shapes.AddShape(Type:=msoShapeRectangularCallout, _
Left:=Rng.Information(wdHorizontalPositionRelativeToPage), _
Top:=Rng.Information(wdVerticalPositionRelativeToPage) - Hght, _
Width:=Wdth, Height:=Hght, Anchor:=Rng)
.Tables.Add Range:=Shp.TextFrame.TextRange, Numrows:=1, numcolumns:=2
Shp.TextFrame.TextRange.Characters.Last.Font.Hidden = True
End With
Application.ScreenUpdating = True
End Sub