Would it work to collect the number of entities department from entity generation and the number of entities arrived from the entity sink (using the Statistics ports) data in MATLAB for multiple simulation runs and then use that as a distribution to find the probability? Are you trying to do this through simulation? I guess you can query the blocks through get_params in MATLAB to find delays in the system and calculate it that way as well? Let me know if this helps. I think I need to know more about your goals.