A Differential Equations model with S-function Level 2

Hi, I would like to model the following system using a S-function level 2 block:

dV_dt=w*(pi*(d^2)/4)*(R+sin(theta)+(R^2)*sin(theta)*cos(theta)/(L*sqrt(1-(R^2)*(sin(theta)^2)/(L^2))))

w, d, R, THETA, and L are inputs, parameters or constants. I have written the following file but I do not obtain the expected results. I just want to obtain V, and dV_dt as outputs. Another question is how I can define R, L, d as constants inside the S-function instead of defining as parameters.

file:

function GeometriaCil(block) % Level-2 MATLAB file S-Function for basic integrator demo. % Copyright 1990-2009 The MathWorks, Inc.

setup(block);

%endfunction

function setup(block)

%%Register number of dialog parameters   
block.NumDialogPrms = 3;

%%Register number of input and output ports
block.NumInputPorts  = 2;
block.NumOutputPorts = 1;

%%Setup functional port properties to dynamically
%%inherited.
block.SetPreCompInpPortInfoToDynamic;
block.SetPreCompOutPortInfoToDynamic;

block.InputPort(1).Dimensions        = 1;
block.InputPort(1).DirectFeedthrough = false;

block.OutputPort(1).Dimensions       = 1;

%%Set block sample time to continuous
block.SampleTimes = [0 0];

%%Setup Dwork
block.NumContStates = 1;

%%Set the block simStateCompliance to default (i.e., same as a built-in block)
block.SimStateCompliance = 'DefaultSimState';

%%Register methods
block.RegBlockMethod('InitializeConditions',    @InitConditions);  
block.RegBlockMethod('Outputs',                 @Output);  
block.RegBlockMethod('Derivatives',             @Derivative);

%endfunction

function InitConditions(block)

%%Initialize Dwork
block.ContStates.Data(1) = 0;

%endfunction

function Output(block)

block.OutputPort(1).Data = block.ContStates.Data;

%endfunction

function Derivative(block) R = block.DialogPrm(1).Data; L = block.DialogPrm(2).Data; d = block.DialogPrm(3).Data;

   theta =  block.InputPort(1).Data;
   w =  block.InputPort(2).Data;
   f1=(pi*(d^2)/4)*(R+sin(theta)+(R^2)*sin(theta)*cos(theta)/(L*sqrt(1-(R^2)*(sin(theta)^2)/(L^2))));

       block.Derivatives.Data(1) = f1*w; %dV_dt

%endfunction

Greetings,

Carlos