Getting control from popup window to called window.

I have  created a Progress bar  by   calling  my long server side process in a new thread and call a popup progress.aspx page to  shows the progress..

progress value is stored in  static class file called CProgressArg

code in the progress.aspx  file is like this

int state = CProgressArg.percn;

protected void Page_Load(object sender, EventArgs e)

{

if (state > 0 && state <= 100)
{

this.panelProgress.Width = (400 * state) / 100;
this.lblPercent.Text = state + "%";
Page.ClientScript.RegisterClientScriptBlock(typeof(Page), "", "<script>window.setTimeout('window.form1.submit()',1000);</script>");

else
{

this.lblMessages.Text = "Error Ocoured!";
Page.RegisterStartupScript("", "<script>window.close();</script>");
return;

}

}

I called new thread like this in the button click in main page.

new Thread(delegate()
{
ProcessModule(dtemp, ref errmsg);
}).Start();

below code will open the progress.aspx page.

ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "", "OpenProgess('../Payroll/Progress.aspx', 0,420,150);", true);

After executing full function  in new thread I need to show another popup that "Want to procees  next activity " . this msg has to be in main aspx page from where i create thread....

How can i get back to main page from  progress.aspx  if all process finishe.???

Or can i Popup window as ajax modal popup  instead of another aspx page (like progress.aspx)..

If we can then How to show the progress in modal popup window ??