How to sum array elements in a for loop in Stateflow C action language

I tried everything I could think of, it seems the Stateflow C action language does not recognize "for" loop, the only way I can make it work is :

entry: sum = a[0] + a[1] + a[2] + a[3];

avg = sum / count;

But what if I don't know count ahead of time, what do I do ?