In Simulink, how can I execute a subsystem once every 5 seconds?

In Simulink, how can I execute a subsystem once every 5 seconds? While the rest of the simulation will need smaller time steps, I would like one subsystem to only execute once every 5 seconds and then hold that output value of the subsystem for the remainder of the 5 second period.

I tried to do this using triggered subsystems. However, I got an error because my subsystem has continuous blocks (Fourier blocks). Basically, I just want my Simulink model to do a Fourier analysis of voltages/currents in my model once every 5 seconds and not continually recompute this with every small time step that is needed for simulation of the electrical system.

[Dimitris Iliou]

Could you share your model in order to see what kind of blocks do you use?