You could use something like the following which will set no border and fill the cells with a light grey shading for all tables. Change or add whatever else you need in the FormatTable macro.
Code:
Sub UpdateAllTables()
Dim oStory As Range
Dim oTable As Table
For Each oStory In ActiveDocument.StoryRanges
For Each oTable In oStory.Tables
FormatTable oTable
Next oTable
If oStory.StoryType <> wdMainTextStory Then
While Not (oStory.NextStoryRange Is Nothing)
Set oStory = oStory.NextStoryRange
For Each oTable In oStory.Tables
FormatTable oTable
Next oTable
Wend
End If
Next oStory
Set oStory = Nothing
lbl_Exit:
Exit Sub
End Sub
Private Sub FormatTable(oTable As Table)
With oTable
.Borders.OutsideLineStyle = wdLineStyleNone
.Shading.BackgroundPatternColor = wdColorGray10
End With
lbl_Exit:
Exit Sub
End Sub