You can pass the value back over the vi's terminals back to the vi's caller, from where you pass it also back over the terminal.
You could also use the reference, but this is usually just necessary, if there is an action to take place in the main vi while the sub vi is executing. If possible, avoid it and try to use the dataflow.
This are just two possible ways, but there are much more. Every way with its advantages and disadvantages.
Do you mean to say that:
If I have a sub-vi executing a while loop, with the iteration passed to a numeric indicator on the FP of the sub-vi, I can show the iteration count on my main-vi by simply passing the sub-vi's numeric indicator's reference to another numeric indicator on the front panel of my main-vi? And this will happen even while my sub-vi's While Loop is still executing?
Sorry if my small aside interrupted the real thread.