Попробуйте что-нибудь на основе:
Sub Demo()
Application.ScreenUpdating = False
Dim r As Long
With ActiveDocument.Tables(1)
For r = 2 To .Rows.Count
With .Rows(r)
If .Cells.Count > 3 Then .Cells(4).Delete
End With
Next
End With
Application.ScreenUpdating = True
End Sub