Does anyone know how to access the productid in a catalook productlist.

I'm trying to do this using a usercontrol, but I don't know how I can get the productID:

        Private _ProductID As Integer

        Public Sub New()
            Me._ProductID = -1
        End Sub

        Public Property ProductID() As Integer
            Get
                Return Me._ProductID
            End Get
            Set(ByVal Value As Integer)
                Me._ProductID = Value
            End Set
        End Property

        Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
            Dim CategoryID As Integer = Request.QueryString("CategoryID")
            lblLight.Text = "<a href='http://omax/Producten/Catalogus/tabid/65/CategoryID/" & CategoryID & "/List/1/Level/a/productid/" & ProductID & "/Default.aspx' rel=""lyteframe[{groupname}]"" rev=""width: 400px; height: 300px; scrolling: no;"" title=""Titel"">Plaatje  test</a> "
        End Sub

Always ends up with -1 for productid...