APS.NET 1.1にて2つの画面の処理を並列で行ないたい。

Public Class testtesttest
    Inherits System.Web.UI.Page
    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' ポップアップ画面起動
        Me.Button1.Attributes.Add("onclick", "wn=window.open('popup/popup_wait.aspx');wn.focus();")
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            'ループを行い遅い処理を演出
            For i As Int32 = 1 To 9999
                For j As Int32 = 1 To 9999
                    For k As Int32 = 1 To 9999
                    Next k
                Next j
            Next i
            Me.Label1.Text = "処理終了"
        End Try
    End Sub
End Class