MATLAB: If I can set the output of memory block during simulation

memory blockset_paramsimulink

I use memory block to record the number of iteration. Anyway, when the iteration gets a threshold, I want to set the value of memory back to zero, and do the sum up again. Now I'm thinking about using 'set_param' in m file to control the value of memory. But I don't know how to change the value of memory. I think change the input and output of memory block also works for me.
Could anyone help me?
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