In an attempt to work around the bug that stops me from being able to pass a new form or subform row to a function, I'm trying to use formula fields instead. However, because I can't reference a formula field in another formula field I'm having to try and do the above formula in the parent form, when this is the formula in the subform. How do I make it work? 

As the application is under constant development, please can you repro on your end and then provide a working sample application/example formula please.