create a stochastic variable

 i would like to create the stochastic variable I which are part of the equation dx/dt=-x+I(t)
I(t)=0.075,t=t1
I(t)=-0.072,t=t2
which t1,t2 follow poisson distribution. 
i follow the next M-file but there is a mistake!
h=0.0001;              
t1=0;
k=0;
    while t1<0.3
          k=k+1;
          t1=t1-0.015*log(rand(1));t1s(k)=t1;
    end
t2=0;
c=0;
while t2<0.3
    c=c+1;
    t2=t2-0.015*log(rand(1)); t2s(c)=t2
end
t=0;
z=0;
while t<0.3
    z=z+1;
    t=t+h;
    ts(z)=t;
end
I=0;
    for l=1:z
        for j=1:c
            for i=1:k
    if abs(ts(l)-t1s(i))<1e-5
        I=I+0.075*h;
    elseif abs(ts(l)-t2s(j))<1e-5
        I=I-0.072*h;
    end
            end
        end
    end

[Walter Roberson]

What "mistake" do you observe? Is there an error message?