Dim sBuffer As String
 
    Private Sub DataGridView1_CellBeginEdit(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.DataGridViewCellCancelEventArgs) Handles _
      DataGridView1.CellBeginEdit
        If e.ColumnIndex = 0 Then
            sBuffer = DataGridView1.Item(e.ColumnIndex, e.RowIndex).Value
            If sBuffer = String.Empty Then
                sBuffer = "0"
            End If
        End If
    End Sub
 
    Private Sub DataGridView1_CellValidated(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.DataGridViewCellEventArgs) Handles _
      DataGridView1.CellValidated
        If e.ColumnIndex = 0 Then
            Dim s As String = DataGridView1.Item(e.ColumnIndex, _
              e.RowIndex).Value
            If s = String.Empty Then
                DataGridView1.Item(e.ColumnIndex, e.RowIndex).Value = 0
            Else
                If s.Length <> 1 Then
                    DataGridView1.Item(e.ColumnIndex, e.RowIndex).Value = _
                      sBuffer
                Else
                    If s <> "0" And s <> "1" And s <> "2" And s <> "3" And s <> "4" _
                            And s <> "5" And s <> "6" And s <> "7" And s <> "8" Then
                        DataGridView1.Item(e.ColumnIndex, e.RowIndex).Value = _
                          sBuffer
                    End If
                End If
            End If
        End If
    End Sub