Dim popupScript As String = "window.open('cFinder.aspx?cName=" & c_TextBox.Text & "','', 'width=420,height=200,menubar=no,scrollbars=yes');"
If (Not Page.ClientScript.IsStartupScriptRegistered("popup")) Then
Page.ClientScript.RegisterStartupScript(Me.GetType(), "popup", popupScript, True)
End If

    Public Sub Redirect(ByVal url As String, ByVal target As String, ByVal windowFeatures As String)
        Dim context As HttpContext = HttpContext.Current
        If ([String].IsNullOrEmpty(target) OrElse target.Equals("_self", StringComparison.OrdinalIgnoreCase)) AndAlso [String].IsNullOrEmpty(windowFeatures) Then
            context.Response.Redirect(url)
        Else
            Dim page As Page = DirectCast(context.Handler, Page)
            If page Is Nothing Then
                Throw New InvalidOperationException("Cannot redirect to new window outside Page context.")
            End If
            url = page.ResolveClientUrl(url)
            Dim script As String
            If Not [String].IsNullOrEmpty(windowFeatures) Then
                script = "window.open(""{0}"", ""{1}"", ""{2}"");"
            Else
                script = "window.open(""{0}"", ""{1}"");"
            End If
            script = [String].Format(script, url, target, windowFeatures)
            ScriptManager.RegisterStartupScript(page, GetType(Page), "Redirect", script, True)
        End If
    End Sub

            Session.Item("ObjToRedirect") = TextBox1.Text
            Redirect("NextPage.aspx", "_blank", "width=200,height=200,menubar=no,scrollbars=yes")