Running Excel VBA functions(macros) from MATLAB using a parfor loop

I am trying to perform a particle swarm optimization (PSO) in which I require MATLAB to be interfaced with Excel VBA. Each particle is linked to an individual Excel Workbook. I have been able to successfully carry out a function call to Excel while using a for loop. However when I use a parfor loop, I get the following error: "Cannot run the macro 'Output'. The macro may not be available in this workbook or all macros may be disabled".

Below is a sample code:

Np = 3 % Number of particles

for i = 1:Np Excelpar(i) = actxserver('Excel.Application'); Workbook(i) = Excelpar(i).Workbooks.Open(workfile{i},1,true); % workfile{i} indicates the path of % the Excel workbook Excelpar(i).visible = false; Excelpar(i).DisplayAlerts = false; end

parfor k = 1:Np % I have no problems when this is a for loop c = zeros(1,6); c = Excelpar(k).Run('Output',x(k,1), x(k,4), Feed_B(k), x(k,5), x(k,2), x(k,3), P(k)); end

Any help provided is warmly appreciated Thanks