Simulink - output mean value of last X signal values

I want to create a subsystem in Simulink that has one signal input. The simulation is fixed-step. On the first step, the subsystem should output the value of the input signal. On the second step, the subsystem should output the mean value of the current and previous signal values with weighted parameters (for example: (0.5*IN1+1.5*IN2)/(0.5+1.5)). On the third step, the subsystem should output the mean value of the first, previous and current signal values with weighted parameters, and so forth.

I want to calculate the mean value according to the last 15 output only.

Is there a simple way to accomplish this is Simulink?