Hi Arne,

Like as answer: http://www.telerik.com/support/kb/article/b454K-hce-b454T-a-b454c-cbetemdget.aspx
Or simply check you test box changes for digitals: http://www.dotnetspider.com/code/C-550-Numeric-Text-Box-Accept-only-numbers.aspx 
(the OnKeyPress method is enough for instance)

Regards, Alex
[TechBlog] http://devkids.blogspot.com

Try this:

Public Class NumericTextBox
   Inherits TextBox

   Private Const ES_NUMBER As Integer = &H2000

   Protected Overrides ReadOnly Property CreateParams() As
System.Windows.Forms.CreateParams
       Get
           Dim params As CreateParams = MyBase.CreateParams
           params.Style = params.Style Or Win32.Native.ES_NUMBER
           Return params
       End Get
   End Property

   Protected Overrides Function ProcessCmdKey(ByRef msg As
System.Windows.Forms.Message, ByVal keyData As System.Windows.Forms.Keys) As
Boolean
       'Prevent pasting of non-numeric characters
       If keyData = (Keys.Shift Or Keys.Insert) OrElse keyData =
(Keys.Control Or Keys.V) Then
           Dim data As IDataObject = Clipboard.GetDataObject
           If data Is Nothing Then
               Return MyBase.ProcessCmdKey(msg, keyData)
           Else
               Dim text As String =
CStr(data.GetData(DataFormats.StringFormat, True))
               If text = String.Empty Then
                   Return MyBase.ProcessCmdKey(msg, keyData)
               Else
                   For Each ch As Char In text.ToCharArray
                       If Not Char.IsNumber(ch) Then
                           Return True
                       End If
                   Next
                   Return MyBase.ProcessCmdKey(msg, keyData)
               End If
           End If
       Else
           Return MyBase.ProcessCmdKey(msg, keyData)
       End If
   End Function
End Class

   /claes