cumulative distribution function Trinomial Distribution

%Hello every one,

how i can calculate cumulative distribution function(cdf) for Trinomial Distribution

function ff=myTrinomial(n,p01,p02)

 sum=zeros;

for x=0:n

    for y=0:n-x

    ff(x+1,y+1)=(factorial(n)/(factorial(x)*factorial(y)*factorial(n-x-y)))*p01^x*p02^y*(1-p01-p02)^(n-x-y);

% ff(x+1,y+1)=1-sum(x+2,y+2) end % b=cumsum(ff) end