var p = new Array('ptexte','ptexte2','ptexte3','ptexte4');
    var a = 0;
    var ec = 0;
    
    function fin()
    {
      ec=0;
    }
    
    function set_first(pid)
    {
      var tmp;
      var i = p.indexOf(pid);
      var gto = i * 190;
      if(i && !ec)
      {
      ec=1;
      new Effect.Move(pid, {y:-gto}); 
      new Effect.Move(p[0], {y:gto,afterFinish:fin}); 
      tmp = p[0];
      p[0] = p[i];
      p[i] = tmp;
      }
    }
    
    function suivant()
    {
      a++;
      if(a>3)
        a=1;
      set_first(p[a]);
      return false;
    }
    
    function precedent()
    {
      a--;
      if(a<1)
        a=3;
      set_first(p[a]) ;
      return false;
    }