Private Sub Button1_Click(sender As Object, e As EventArgs) Handles _
  Button1.Click
 
        Dim Label(30) As Label
        'Referenz-Variable
        Dim lbl As Label
        'Alle Controls auf der Form 
        For Each ctl As Control In Me.Controls
            'Labels deren Name mitL beginnt filteren
            If TypeOf ctl Is Label AndAlso ctl.Name.StartsWith("L") Then
                'Control als label casten
                lbl = DirectCast(ctl, Label)
                Label(CInt(lbl.Name.Substring(1))) = lbl
            End If
        Next ctl
 
        Dim sum As Decimal
        For i As Integer = 1 To 30
            Label(i).BackColor = Color.Red
            If CDec(Label(i).Text) <= 0 Then Label(i).BackColor = Color.Green
            sum += CDec(Label(i).Text)
        Next i
 
        Dim mw As Decimal = sum / 30
 
    End Sub
End Class