Basing a function on another function (nesting functions)?

I am new to Hyperion Financial Reporting Studio, so please be gentle.

Is it possible to build a function which uses the result of another function?  Another way to put this is "Is there a way to nest functions?".

I would like to build a function that returns the relativemember -1 of a parent of the POV month.  It seems like this should be possible.  In English, I think it would look something like this:

"Relative to Parent of Current Point of View for Month offset by -1"

That requires two functions, as far as I can tell - and I can't figure out how to do this.