Create a 1Hz trigger (e.g. Pulse Generator with amplitude of 1 and period of 1), feed it to a "Not" block and then an "Assertion" block. The simulation will pause automatically every 1 second.
Uncheck "Stop simulation when assertion fails". add the below lines as the simulation callback
set_param(...);
set_param('ModelName','SimulationCommand','update');
set_param('ModelName','SimulationCommand','continue');
Note that the Pulse Generator may trigger more pauses if the step size is less than 0.05. The point is to make a 1Hz trigger based on your simulation settings.