how do i get a form to upload a file to be attached to an e-mail

i have a pre-bult form that can be filled out and submited. when it get submited it sends a text e-mail with the information of all the fields in it. i want users to be able to upload a .doc file that gets attached to the e-mail that gets sent out. im pretty sure i have the code for it i just dont know how to set it up. this is part of whats in my formmail.php file

// check for a file if there is a file upload it

if ($file_name) {

   if ($file_size > 0) {

      if (!ereg("/$", $path_to_file))

         $path_to_file = $path_to_file."/";

      $location = $path_to_file.$file_name;

      if (file_exists($path_to_file.$file_name))

         $location .= ".new";

      copy($file,$location);

      unlink($file);

      $content .= "Uploaded File: ".$location."\n";

   }

}