UI not responding while Downloading a file using Response.Write

On my page I have a Lable1 and Button1. On Button1 click I am doing the following to push a file to client and change the text on the button and lable. File is getting downloaded, but the UI changes or not happening. What is the simplest solution to force the UI changes?
        protected void Button1_Click(object sender, EventArgs e)         {             string filePathName = string.Format("{0}\\{1}", Request.PhysicalApplicationPath, "SmallBiz_Guide.pdf");             HttpContext.Current.Response.AppendHeader("content-disposition",                 "attachment; filename=" + Path.GetFileName(filePathName));        &nbs ...