function numbersonly(myfield, e, dec)
{
var key;
var keychar;

if (window.event)
   key = window.event.keyCode;
else if (e)
   key = e.which;
else
   return true;
keychar = String.fromCharCode(key);

// control keys
if ((key==null) || (key==0) || (key==8) || 
    (key==9) || (key==13) || (key==27) )
   return true;

// numbers
else if ((("0123456789").indexOf(keychar) > -1))
   return true;

// decimal point jump
else if (dec && (keychar == "."))
   {
   myfield.form.elements[dec].focus();
   return false;
   }
else
   return false;
}

function getCheckedValue(radioN) {
  radioObj = document.getElementsByName(radioN);
	if(!radioObj)
		return "";
	var radioLength = radioObj.length;
	if(radioLength == undefined)
		if(radioObj.checked)
			return radioObj.value;
		else
			return "";
	for(var i = 0; i < radioLength; i++) {
		if(radioObj[i].checked) {
			return radioObj[i].value;
		}
	}
	return "";
}
 
function prepocitejCenuObj() {
      cena = document.getElementById('cena_celkem_obj');
      cenapol = document.getElementById('cena_celkem');
      radio_1 = document.getElementById('radio_doprava');
      val = parseInt(cenapol.value);            

      doprava = getCheckedValue ("zpusobdopravy");
      val2 = parseInt(arr_ceny_dopravy[doprava]);  
        
      vall = val + val2;
      cena.innerHTML = vall;
      
}