Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles _
      DataGridView1.CellValidating
        Dim dt As DataTable = dieDataTable
        If dt.Columns(e.ColumnIndex).DataType Is GetType(Integer) Then
            Dim vok As Boolean
            Integer.TryParse(e.FormattedValue, vok)
            If Not vok Then
                MsgBox("Wert falsch!")
                e.Cancel = True
            End If
        End If
    End Sub

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov