How to change commission and spread during the backtest?

How to backtest system if the spead of the instrument is 0.02% and the commission is 0.03%?

Are Commission and Spread valiables fixed during the backtest?

Is it possible to change it with TMF?

You can compute the actual values and assign them in the backtest loop using these parameters:

http://zorro-project.com/manual/en/spread.htm