how to make cycles in simulink?

I want to create a system, which is in a circle. I assume certain initial conditions for let's say X and Y, which are variables. After they reach a specific value I want them to them to take this value as new initial condition. Then calculations start again.

In my case X and Y are in Z-Domain, so I set initial conditions in Unit Delay Block. I thought maybe to use Sybsystem, but I'm not sure how to do this.