Implied Volatility for Futures Contracts

["DC" <dc010225@xxxxxxxxxxxxx>]

I am trading Options on Futures contracts at Man Financial.
I am also exploring to trade Options on E-Mini Russell 2000 Futures electronic contracts 
at TradeStation Securities.

Problem is that Implied Volatility (IVolatility, see bellow) is not working for Futures 
contracts. It works only for stocks. So I cannot compute the synthetic prices of Call and 
Put options and backtest my option selling strategies.

Question: Do you know why it is not working and when it will be fixed?

DC
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>From TradeStation 8.1 User Guide:

IVolatility (Reserved Word)

Returns the daily average weighted Implied Volatility of the options for an underlying 
stock, index, or future.  Allows historical data (bars back) references.

Example:

Value1 = IVolatility;

or

Value2 = IVolatility[2]     // of two bars ago