function fnNumeros(myfield, e) {
	if (myfield.length ==0)
		myfield.value=0;  
	var key;
	var keychar;
	if (window.event)
	     key = window.event.keyCode;
    else if (e)
		key = e.which;
    else
		return true;
	keychar = String.fromCharCode(key);
    if ((key==null) || (key==0) || (key==8) || (key==9)|| (key==13)|| (key==27) )
		return true;
	else if ((("0123456789").indexOf(keychar) > -1))
		return true;
	else
	return false;
}