From the Online Manual

Code
contractVol (CONTRACT*, var Price, var HistVol, var Value, var Dividend, var RiskFree): var


Returns the implied volatility (IV) of the given option contract with the given Value. For the parameters, see contractVal. The function uses R and the RQuantLib package; both must be installed on the trading PC (see remarks below). Source code in contract.c. The implied volatility is an estimate of the future volatility of the underlying, based on the current option parameters. If the contract has no value or if the strike price is too far or on the wrong side of the asset price, the function returns 0.

Fine and good that the implied volatility or open interest is a variable. It means that it can be easily plotted using the plot function.


Code
contract (int Type, int Expiry, var Strike): CONTRACT*
var Price = priceClose();
var HistVol = VolatilityOV(20);
var Value = ?
var Dividend = 0.02;
var RiskFree = 0.01*yield();


Need further directions please.