Not exactly sure what you mean. Assuming that you intend to run the Simulink model, you will probably use the SIM command which only returns to MATLAB after simulation is complete. However, if you are click play on the model and want to query the status, you can use: get_param('modelname', 'SimulationStatus') - it returns "stopped" when the simulation is done.
There is no determinate way of predicting how long a simulation takes in real-time, because it depends on a variety of factors like system performance and Simulink solver settings.
