Public Class MeineTextBoxKlasse
    Inherits TextBox
 
    Public Sub New()
        AddHandler Me.KeyPress, AddressOf HandleKeyPress
    End Sub
 
    Private Sub HandleKeyPress(ByVal sender As Object, ByVal e As _
      KeyPressEventArgs)
        If IsNumeric(e.KeyChar) Or _
             e.KeyChar = "," Or _
             e.KeyChar = "." Or _
             e.KeyChar = ":" Then
            e.Handled = False
        ElseIf Not Char.IsDigit(e.KeyChar) And Not Char.IsControl(e.KeyChar) _
          Then
            e.Handled = True
        End If
    End Sub
 
End Class