Portfolio Backtesting - Rolling Window

Hello everyone! My first post here. Basically, I am quite new to Matlab and what I am trying to accomplish is to create a rolling window. I have monthly data from Dec 89 to Dec 2013 and I would like to create a 6 month rolling window to compute each covariance and use it in a portfolio model. I can't do that manually since these are around 38 covariance matrices and I would test 3 different portfolio strategies.

I am afraid that is all I can provide since I am relatively new so all help is well appreciated.

P.s I have looked at the slidefun function but I am not entirely sure whether it will help me.

Thanks in advance!