parfor loop variable cannot be classified

I'm trying to create a function that will select each column from a 1X30 cell and set the velocity value to the mean(defined as a 1X30 cell from another function), but I keep getting "The variable A in a parfor cannot be classified"

function [A]=set_vel(cell, mean)

A={};

parfor i=1:length(cell)

 for j=1:length(mean)
       A{i,j} = setvalues(cell{i},'vel', mean{j});
    end
end

Can someone help?

[mzaya]

Oh just figured it out. Here is what I did:

A={};

parfor i=1:length(cell)

    M{i} = mean(cell{i}(:,5));

    A{i} = setvalues(cell{i},'vel',  M{i});
    end
end