Public Class test
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    End Sub

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim newwindow As New Telerik.Web.UI.RadWindow
        newwindow.NavigateUrl = "~/UserControls/Dialogbox.aspx"
        newwindow.ID = "RadWindow1"
        newwindow.VisibleOnPageLoad = True
        RadWindowManager1.Windows.Add(newwindow)
    End Sub
End Class