currency={'usd': '2.24','gbp': '1.43','eur': '1.71','jpy': '172.83','brl': '3.9','rub': '68.06','pln': '7.23'};

function currency_convert () {
  cForm  = document.getElementById('currency_form');
  var result = ((cForm.amount.value / currency[cForm.from.value]) * currency[cForm.to.value]);
  cForm.result.value = (Math.round(result*100)/100) + ' ' + cForm.to.value.toUpperCase();
  return false;
}