var submitInterval = null;
var enterField = null;
var enterFieldValue = null;
var enterFunc = "tryLogin()";
function checkSubmit(){
  window.clearInterval(submitInterval);

  if ( enterField.value == enterFieldValue )
  {
    eval(enterFunc);
  }
}

function checkEnter(field, e){ //e is event object passed from function invocation
  var characterCode; // literal character code will be stored in this variable

  if(e && e.which){ //if which property of event object is supported (NN4)
    characterCode = e.which; //character code is contained in NN4's which property
  } else{
    characterCode = e.keyCode; //character code is contained in IE's keyCode property
  }
  if(characterCode == 13){ //if generated character code is equal to ascii 13 (if enter key)
    enterFieldValue = field.value;
    enterField = field;
    submitInterval = window.setInterval("checkSubmit()",50);
  }
  return true;
}
function checkEnterFunc(field, e, func) { //e is event object passed from function invocation
  enterFunc = func;
  checkEnter(field, e);
}