Matlab: optimize code

string3=TrajSimilarity(1,3).aLongestString;
string4=TrajSimilarity(1,4).aLongestString;
[D,dist,aLongestString]=LCS(string3,string4);

U=numel(regexp(string3,'(\(\d+\)|\d)'));
V=numel(regexp(string4,'(\(\d+\)|\d)'));
nLCS=numel(regexp(aLongestString,'(\(\d+\)|\d)'));

ratioU=nLCS/U;
ratioV=nLCS/V;

EA = (ratioU + ratioV)/2;
WA = (U*ratioU+V*ratioV)/(U+V);

LCS is a function that calculates the longest common substring between two strings (if can be helpful, I will post a link with it). I have problems to create an optimized code that compare the longest common sequence of the first user with the others, the longest common sequence of the second user with the others and etc. I try this code:

for k=1:14
   string3=TrajSimilarity(1,k).aLongestString;
    for j=2:14
        string4=TrajSimilarity(1,j).aLongestString;
        [A(k,j).D,A(k,j).dist,A(k,j).aLongestString]=LCS(string3,string4);
    end
end

but it generates error: