how can I use power of 24 cores in matlab?

I want to use full power of my G9 server (has 24 cores and 64GB RAM) to run a matlab script.

My test code heres (original code is complex but it's like this):

s=0;
parfor i=1:10000
    for j=1:10000
        for k=1:10000
            s=s+i;
        end
    end
end
disp(s);

CPU usage is 25%.

how can I use power of 24 cores in matlab and improve CPU usage to 50% or higher?

[Walter Roberson]

Did you configure a pool and use parpool to open the pool?