document.onkeydown = getKeycode;
 
var enable_enter = false;
var blnDOM = false, blnIE4 = false, blnNN4 = false; 
 
if (document.getElementById) blnDOM = true;
else if (document.layers) blnNN4 = true;
else if (document.all) blnIE4 = true;
 
function state_enter_key(str)
{
 if(str = "on") 
 {
  enable_enter = true;
 }
 else
  enable_enter = false;
 
}
 
function getKeycode(e)
{
 if(!enable_enter)
 {
   if (blnNN4)
   {
     var mykey = e.which;
   }
 
 
   if (blnDOM || blnIE4)
   {
     var mykey = event.keyCode;
   } 
 
   if (mykey ==13)
  return false;
 }
}