Private Sub txtKonzentration_KeyPress(ByVal sender As System.Object, _
        ByVal e As System.Windows.Forms.KeyPressEventArgs) _
        Handles txtKonzentration.KeyPress
 
        If e.KeyChar = Microsoft.VisualBasic.ChrW(13) Then
            Dim myTextBox As New TextBox
            Dim nummer As Integer
            nummer = sender.Tag + 1
            myTextBox.Name = "txtMesswert" & nummer
            If existenz(pnlMesswerte, myTextBox.Name) = False Then
                myTextBox.Left = txtMesswert.Left
                myTextBox.Top = 20 * nummer
                myTextBox.Tag = nummer
                AddHandler myTextBox.KeyPress, AddressOf txtMesswert_KeyPress
                pnlMesswerte.Controls.Add(myTextBox)
            End If
        End If
    End Sub
 
    'Checkt lediglich ob eine bestimmte Textbox schon vorhanden ist
    Private Function existenz(ByVal checkCtrl As Object, _
        ByVal checkName As String) As Boolean
 
        Dim ctrl As Control
        existenz = False
        For Each ctrl In checkCtrl.controls
            If ctrl.Name = checkName Then
                existenz = True
            Else
                existenz = False
            End If
        Next
    End Function

Gru? Patrick
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Wer nicht fragt, bleibt dumm.