Since you use C0 as a start-value, it is required to be a parameter expression. Parameter expressions can never change, so what you try to do is impossible.

You can probably do this using bindings and maybe you need reinit and when equations.
It depends if you have continuous variables or discrete ones.

Real C0 = somevalue;

Real C[N] = fill(C0, N) ;

equation

when time > 10 then

  reinit(C0, someothervalue);

end when;

// for loop ...

Thank you!

Is there some function like 'xlsread' and "xlswrite" in matlab?
Since I want to simulate a large number of loops, and the result of step j is the initialization of step j+1
Do you have any idea about this?

Because my model is very complex consisting of 21 partial differential algebraic equations, and I want simulate it for hundreds of cycles, I cannot update the initial values by hand.

Could you give me some suggestion?