You Look Too Cool

Sub 選択範囲内の罫線の太さを変える()
  Dim border_index As Integer
  Dim border_weight As Integer
  Dim res As String
  Dim mycell
  Const maxrow = 100
  Const maxcol = 100
  Const str = "線の太さ。1-極細、2-細、3-中、4-太"
  res = InputBox(str, "太さ", 2)
  If res = "" Then
    Exit Sub
  End If
  border_weight = CInt(res)
  If border_weight > 4 Or border_weight < 1 Then
    MsgBox ("線の太さが範囲外。")
    Exit Sub
  End If
  If Selection.rows.Count > maxrow Or Selection.Columns.Count > maxcol Then
    res = MsgBox("範囲が広いので" & maxrow & "行×" & maxcol & "列を処理。", vbOKCancel)
    If res = vbCancel Then
      Exit Sub
    End If
    Range(Cells(1, 1), Cells(maxrow, maxcol)).Select
  End If
  For Each mycell In Selection
    For border_index = 7 To 10 'セルの4辺(左上下右)
      If mycell.Borders(border_index).LineStyle <> xlLineStyleNone Then
        mycell.Borders(border_index).Weight = border_weight
      End If
    Next border_index
  Next mycell
End Sub