I was able to get the ItemPK from the querystring. RenderUserControl is very cool.
public void BindUpsellList() { busItem Item = WebStoreFactory.GetbusItem(); if (ItemPk == 0) { string Sku = Request.QueryString["Sku"]; if (!string.IsNullOrEmpty(Sku)) ItemPk = Item.GetPkFromSku(Sku); } int Result = Item.GetUpsellItems(ItemPk, "TUpsell"); if (Result > 0) { repUpsellList.DataSource = Item.DataSet.Tables["TUpsell"]; repUpsellList.DataBind(); } else Visible = false; }