That is not possible within the functionality of a for-loop (which is what a For-Iterator is). If it would be possible, the execution of the whole for-loop would not be deterministic, and that's bad.
What you can do, is execute the For-Iterator Subsystem in a lower sample rate, for example one which is twice as slow. Then, the results will only be ready after two iterations of your main loop. Then you will need to use Rate Transition blocks to make handle reading and writing of signals in between the two sample rate tasks.