addhandler事件触发不了 高手进来！！

我做了一个下拉框，选择后触发生成一个下拉框，当我扑捉新生成的下拉框的时候用addhandler，但是却扑捉不了，请高手解释！！一下是简化  代码
Protected Sub ddlBelongs123_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlBelongs123.SelectedIndexChanged
            Dim dpl1 As DropDownList = New DropDownList
            AddHandler dpl1.SelectedIndexChanged, AddressOf dpp
            Call selectchange(dpl, dpl1)

end sub
    Sub dpp(ByVal sender As System.Object, ByVal e As System.EventArgs)
            MsgBox("sdf")
        End Sub
#Region ""
        Private Function selectchange(ByVal dpl As DropDownList, ByVal dpl1 As DropDownList)

                dpl1.ID = table3.Rows.Count + 1
                upid1.Controls.Add(dpl1)
         “这行是下拉框绑定，我省略了”
        End Function