parfor understands how to handle addition in parallel. Hence you can simply increment a variable as follows,
N=100;
count = 0;
parfor i = 1:N
count=count+1;
end
If this does not work for any reason, you can create a vector of length N, and use it to count whether i-th iteration called disp.
N = 100;
count = zeros([N, 1]);
parfor i = 1:N
% if disp called
count(i)=1;
end
