Solving Coupled Differential Equations

So, I have two programs, a runner and a function. I am fairly new to MATLAB so any help would be nice. I am not getting calculated values for N(:, 2) and N(:, 3).

Runner:

tspan = [0 10];

global B11;

B11 = 10^-6;

N0 = [1; 1; 1];

global B12;

B12 = 2.8*10^2;

global B22;

B22 = 10^-6;

global I;

I = 10^9;

global v0;

v0 = 1.4*10^-20;

[t,N] = ode45(@bimodaltest, tspan, N0);

Nt = N(:, 1) + N(:, 2);

Vt = N(:, 1).* v0;

plot(N(:, 3), N(:,1), N(:,3), N(:,2));

legend('N1','N2');

.

Function:

function dNdt = bimodaltest(t, N);

global B11;

global B12;

global B22;

global r;

global k;

global v0;

if N(1)>0

    r= N(3, :)/((N(2, :))^2 * v0);

else

    r = 2;

    dNdt = [1; 1; 1];

    k = 0;

end

global I;

dNdt(1) = (-.5.*B11)*(r./(r-1)).*(N(1)^2) - B12*N(2).*N(1) + I;

dNdt(2) = (- 0.5*B22).*(N(2)^2) + (0.5.*B11)*(N(1).^2).*(1./(r-1))+I;

dNdt(3) = (.5*B11*(r/(r-1))*(N(1)^2))*v0 + B12*N(1)*N(2)*v0;

dNdt = dNdt';

If you guys could tell me ASAP what's wrong with my code, I'd really appreciate it.

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency