Passing quantity back to originating function

Wondering the best way to pass a quantity value back up a chain of functions. I have an originating function that calls another, and another, etc. to where the final function is 5 steps down from the originating. This is all base NAV. I'm looking for a way to pass a quantity from the final function back to the originating function without changing every function in the thread.

Additional info: What I'm trying to do is pass back the maximum quantity of items that can be assembled through the Assembly module. If the quantity requested is greater than the maximum quantity able to assemble it would reduce that amount.