http://www.mathworks.com/help/toolbox/finderiv/impvbybls.html
impvbybls - Calculate implied volatility using Black-Scholes option pricing model
Syntax
Volatility = impvbybls(RateSpec, StockSpec, Settle,
Maturity, Strike, OptPrice, 'Name1', Value1...)
Arguments
RateSpec
The annualized continuously compounded rate term structure. For information on the interest rate specification, see intenvset.
StockSpec
Stock specification. See stockspec.
Settle
NINST-by-1 vector of settlement or trade dates.
Maturity
NINST-by-1 vector of maturity dates.
OptSpec
NINST-by-1 cell array of strings 'call' or 'put'.
Strike
NINST-by-1 vector of strike price values.
OptPrice
NINST-by-1 vector of European option prices from which the implied volatility of the underlying asset are derived.