certain number of variables for genetic algorithm to change

Hello! I'm trying to use genetic algorithm toolbox in order to find minimum of fitness function. My function F depends on the vector of input variables (integers ranging from 0 to 1) X = [some values that GA will change in order to find minimum of fitness funciton].

The question is "how can I make GA set only certain number of variables in X vector (for example only three 1s X = [0 0 0 1 0 1 0 1 0 0])?" I tried to use while loop inside the function, but when I call a GA using

[X,fval] = ga(@F,6,[],[],[],[],[0 0 0 0 0 0],[1 1 1 1 1 1],[],IntCon)

it seems like it is a infinite looop.

Could anybody help me with that?

Here's the while loop that I tried to use inside my function:

while sum(nonzeros(X))<=3
    %some code
end