How do I use the simulation time as condition in a If statment in a m-File function?

Hi,

I using ODE solver to solve my system, in my function I'm using an If statment, but the control statment depends of time. This is the source code:

function o = system(time,x)

global c_sf k_sf k_tf F_sf c_sr k_sr k_tr F_sr m_uf m_ur m_s lf lr z_rf z_rr j_s

z_sf = x(5) - lf * x(7); dz_sf = x(6) - lf * x(8); z_sr = x(5) - lr * x(7); dz_sr = x(6) - lf * x(8);

% Here is my problem

t = timet;

perturbation = 0.08*(1 - cos(8*pi*t))/12;

% z_rf = 0.4*sign(x(2))*sin(x(1));

% z_rr = 0.2*sign(x(4))*sin(x(2));

if t<= 1.25
 {
      if t<=0.5

        {
            z_rf = 0;
            }
        elseif t>=0.75
                {
                    z_rf = 0;
                    }
        else
            {
                z_rf= perturbation;
                }
        end
      }

        elseif t >= 1.5
            {
                z_rr = 0;
                {
        else
        {
            z_rr = 0.08*(1 - cos(8*pi*t))/2;
            }

end

O(1) = x(2); O(2) = (-( c_sf*(x(2)-dz_sf) + k_sf*(x(1)-z_sf) + k_tf*(x(1) - z_rf)) -F_sf)/m_uf; O(3) = x(4); O(4) = (-( c_sr*(x(4)-dz_sr) + k_sr*(x(3)-z_sr) + k_tr*(x(3) - z_rr)) -F_sr)/m_ur; O(5) = x(6); O(6) = (-(c_sf*(dz_sf - x(3)) + c_sr*(dz_sr - x(4)) + k_sf*(z_sf - x(1)) + k_sr*(dz_sr - x(3))) + F_sf + F_sr)/m_s; O(7) = x(8); O(8) = (-(c_sf*(dz_sf - x(2))*lf + c_sr*(dz_sr - x(4))*lr + k_sf*(z_sf - x(1))*lf + k_sr*(z_sr - x(3))*lr) - F_sf*lf +F_sr*lr)/j_s;

o=[O(1); O(2); O(3); O(4); O(5); O(6); O(7); O(8)];

I use another M-file to run my program an to configurate the ODE solver. But when I used the ODE there is a mistake in the if statement. How do I implement the time simulation in the function? Help me!