currency exchange rate for given date and currency x++

private ExchRate getExchangeRate(AmountMST amountCur , CurrencyCode currencyCode ,Transdate _createdDatetime)
{
ExchRate _exchRate = 0;
ExchrateSecondary _exchrateSecondary = 0;
ExchRatesTriangulation _exchRatesTriangulation = UnknownNoYes::Unknown;
real temp,ret;

temp= Currency::mstAmount(amountCur, currencyCode, createdDatetime, exchRatesTriangulation, exchRate, exchrateSecondary);

if (temp>0 || temp<0)
{
if (temp== amountCur)
ret = 1.0;
else
ret=temp/amountCur;
}
return ret;
}