The Chooser function calculates the theoretical price, sensitivities, the implied volatility, and the implied strike value of a European simple chooser option using Rubinstein’s model. See Multiple Exercise Options for a further explanation.
Chooser 
(ModelStatistic, Asset, Strike, TimeChoose, TimeExpire, Volatility, InterestRate, YieldRate, MarketPrice, TimeFormat, InterestType, YieldType) 
Note: Optional arguments are shown in Italics. MarketPrice is not Optional for the Implied Calculations.
Argument 
Description 
ModelStatistic 
Numeric value indicating the type of function required for the return value: •Theoretical = 1 •Delta = 2 •Gamma = 3 •Theta = 4 •ImpliedVol = 5 •Vega = 6 •Rho = 7 •Psi = 8 •Lambda = 9 •StrikeSensitivity = 11 •ImpliedStrike = 13 
Asset 
The price of the underlying asset. Must be > 0. 
Strike 
The price at which the asset can be purchased if the option is a call or sold if the option is a put. Must be > 0. 
TimeChoose 
The time, expressed in either Days or Years (depending on the TimeFormat value), until the buyer has to choose whether the option is a call or put. Must be 0 < TimeChoose < TimeExpire. 
TimeExpire 
Time, expressed in either Days or Years (depending on the TimeFormat value), until the options expiration. Must be > 0. 
Volatility 
Annualized volatility of the underlying security. Must be > 0. 
InterestRate 
Riskfree interest rate expressed as a percentage. This rate is interpreted as a continuously compounded rate unless otherwise specified in the InterestType argument. Must be > 0. 
YieldRate 
Yield, expressed as a percentage (dividends or interest yield), of the underlying asset price. This rate is interpreted as a continuously compounded rate unless specified otherwise in the YieldType argument. 
MarketPrice 
Optional. The selling price of the option in the marketplace. This input is required when implied volatility and strike are calculated. Price must be > 0. 
TimeFormat 
Optional. Alphanumeric value indicating the format of the time arguments (i.e. TimeExpire). If omitted, Days are used as the default. Specified as either: •Days = 0 or "D" (case insensitive) •Years = 1 or "Y" (case insensitive) 
InterestType 
Optional. Alphanumeric value indicating the type of InterestRate to use when evaluating the option. This value is converted to Continuously Compounded for the calculations. If omitted, a Continuously Compounded rate is used. 
YieldType 
Optional. Alphanumeric value indicating the type of YieldRate to use when evaluating the option. This value is converted to Continuously Compounded for the calculations. If omitted, a Continuously Compounded rate is used. 
Example
Calculate all of functions for a simple chooser option whose asset price 60 days from the chooser date and 90 days from expiration is $62. The exercise price is $65, the riskfree interest rate is 7.5% per annum, the yield rate is 3.5% per annum, and the annual volatility is 25%. All of the rates are considered continuous. So, 
Input 

Output 

Variable 
Value 

Function 
Name 
Value 
Asset 
62 

1 
Theoretical: 
5.941501 
Strike 
65 

2 
Delta: 
0.217452 
TimeChoose 
60 

3 
Gamma: 
0.109761 
TimeExpire 
90 

4 
Theta: 
0.033427 
Volatility 
25% 

5 
Implied Vol.: 
0.252747 
InterestRate 
7.5% 

6 
Vega: 
0.212848 
YieldRate 
3.5% 

7 
Rho: 
0.047894 
MarketPrice 
6 

8 
Psi: 
0.033243 
TimeFormat 
Days 

9 
Lambda: 
2.269132 



11 
Strike Sensitivity: 
0.298824 



13 
Implied Strike: 
65.189774 
For a further example on this model see the included Excel Template located in the root directory of the addin. This example can be accessed through the Multiple Exercise Template menu item after the addin has been installed properly.
A list of all of the possible Error Messages is included for convenience.