AddHandler txbPrimaer.KeyPress, AddressOf OnlyNumeric

Private Sub OnlyNumeric(ByVal sender As System.Object, ByVal e As _
  System.Windows.Forms.KeyPressEventArgs)
 
        Select Case Asc(e.KeyChar)
            Case 48 To 57, 8, 32, 44
                ' Zahlen, Backspace und Space zulassen
            Case Else
                ' alle anderen Eingaben unterdrücken
                e.Handled = True
        End Select
        If CType(sender, TextBox).Text.IndexOf(",") <> -1 AndAlso e.KeyChar _
          = "," Then
            ' Nur ein Komma zulassen
            e.Handled = True
        End If
    End Sub