var move = false;
var position;

var object;
var selectObj;

document.onmouseup = onMouseUp;
document.onmousemove = onMouseMove;

function onMouseDown(obj,select,evnt){
  var e = evnt || window.event
  move = true;
  if (e.clientX)  position = e.clientX;
  else if (e.x) position = e.x;
  object=obj;
  selectObj=select;
}

function onMouseMove(evnt){
  var e = evnt || window.event
  if (move) {
    if (e.clientX){
      ResizeListbox(e.clientX - position, object, selectObj);
      position = e.clientX;
    }else if (e.x){
      ResizeListbox(e.x - position, object, selectObj);
      position = e.x;
    }
    return false;
  }
}

function onMouseUp(){
   move = false;
   window.status='';
}

function ResizeListbox(whereto, ob,sel){
   window.status="entro";

 var begin = document.getElementById(ob).width;
 var intbegin = parseInt(begin);
 var newwidth = intbegin + whereto;
 window.status=document.getElementById(ob).width;
 //Limitamos el resize a 250 como mínimo
 if (newwidth >= 250){
   window.status=newwidth;
   document.getElementById(ob).width = newwidth;
   document.forms['tabla'].elements[sel].width=newwidth;
 }
 document.getElementById(ob).innerHtml=newwidth;
}