Try:
Code:
Sub KillAltText()
Application.ScreenUpdating = False
Dim Rng As Range, Shp As Shape, iShp As InlineShape, i As Long
With ActiveDocument
For Each Rng In .StoryRanges
With Rng
For Each Shp In .ShapeRange
With Shp
If .Type = msoGroup Then
For i = 1 To .GroupItems.Count
.GroupItems(i).AlternativeText = ""
Next
End If
.AlternativeText = ""
End With
Next
For Each iShp In .InlineShapes
iShp.AlternativeText = ""
Next
End With
Next
End With
Application.ScreenUpdating = True
MsgBox "Finished updating", vbOKOnly
End Sub