function doInstall(ext)
{
  var xpi = null;
  
  switch (ext)
  {
    case "equilibre":
      xpi = {
        "EquiLibre 0.2" : {
          URL: "/xpi/equilibre.xpi",
          IconURL: "/xpi/equilibre.png",
          toString: function () { return this.URL; }
        }
      };
      break;
  }
  
  if (xpi != null)
    InstallTrigger.install(xpi);
  else
    alert("Choisissez une extension valide !");
}