Sub Macro2()
Dim oRng As Range
Dim oTable As Table
Dim oBorder As Border
    Set oRng = ActiveDocument.Range
    oRng.Start = Selection.Start
    For Each oTable In oRng.Tables
        For Each oBorder In oTable.Borders
            oBorder.LineStyle = wdLineStyleNone
        Next oBorder
    Next oTable
End Sub