You still have to process each table separately e.g.
Code:
Sub Macro1()
Dim oTable As Table
Dim i As Integer
For Each oTable In ActiveDocument.Tables
oTable.Columns(2).Select
For i = 3 To oTable.Columns.Count
Selection.MoveRight Unit:=wdCharacter, Count:=1, Extend:=wdExtend
Next i
'do something with the selection here
Next oTable 'then move on to the next table
End Sub